Matt,
I am assuming that you have a standard indirect hot water cylinder with 4 pipes entering as described below:
1. hot water to taps out from the top (or near the top)
2. cold water in near the base (from mains or a cold water tank in the loft)
3. hot water from boiler entering at side about half way up
4. return warm water to boiler usually near base.
The tank thermostat usually electrically controls a valve (2 port or 3 port) which opens or closes the flow from the boiler to pipe number 3.
A thermostatic valve as you describe seems very unusual for the boiler primary loop. Are you sure that you do not have an extra (5th) outlet pipe with a thermostatic control for a shower?
Replacing such a valve in such a location will require a full system to be drained unless it has isolating valves either side?
Can you confirm the details of the pipes and control system?
regards
Ian L.
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Ian,
Thanks for replying.
Not at home at the moment so will describe from memory and please bear in mind that I haven't actually taken the insulation off the tank, merely felt around with hands. It's a bit difficult because the shelves in the cupboard are very close to the tank.
1. hot water to taps out from the top (or near the top) - there's a pipe that goes straight out of the top, where it goes after that I don't know.
2. cold water in near the base (from mains or a cold water tank in the loft) - there is a thin pipe that goes in at the bottom, what's odd is that it has a 90 degree bend in it, up to the bend the pipe is hot, after the bend it's cold.
3. hot water from boiler entering at side about half way up - there is a pipe going in halfway up, as described previously with the thermostat.
4. return warm water to boiler usually near base. - don't know.
I do have a shower which is driven by a seperate large pump, I'm not sure which pipe from the boiler supplies it. My earlier comment about the water being a bit less than tepid this morning was based on the shower, so maybe the thermostat in question does control that.
"The tank thermostat usually electrically controls a valve (2 port or 3 port) which opens or closes the flow from the boiler to pipe number 3." I think that I need to try and identify this bit, trouble is I'm not really sure what I'm looking for.
If all of this rather vague information gets us nowhere then I can re-post when I get home.
Getting hold of a plumber at the moment is a job in itself.
Matthew Kelly
No, not that one.
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Matt,
More questions I am afraid.
Is the boiler and CH/HW a sealed and pressurized system or an open (vented) system with expansion and cold water tank in the roof?
Is the hot water cylinder hot to the touch or stone cold?
Also is the pump supplying the shower just for the hot water or both the hot and cold water. If the former then this might be the problem, to eliminate this do you have hot water from any other taps?
regards
Ian L.
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Ian
Is the boiler and CH/HW a sealed and pressurized system or an open (vented) system with expansion and cold water tank in the roof? - it's the latter.
Is the hot water cylinder hot to the touch or stone cold? - stone cold.
Also is the pump supplying the shower just for the hot water or both the hot and cold water. If the former then this might be the problem, to eliminate this do you have hot water from any other taps? - no hot water to taps elsewhere in house (kitchen, bathroom basin etc.)
Hope this helps.
Matthew Kelly
No, not that one.
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Matt,
Last questions!
1. Is the CH working ok? (boiler firing, pump running and radiators getting hot)
2. Do you know what type of circulation of the primary circuit is being used. Older installations can use gravity convection for the HW and pump only cutting in for the CH.....no need for a control valve. Newer installations can use the pump all the time and use a control valve to switch the hot primary circuit water between the hot water cylinder and the boiler.
There is no useful cutoff date of installation to determine which type....old installations can have a newish boiler added and the control system modified.
If you have a gravity convection hw circuit then an airlock or a silted up pipe can cause problems, not much else to go wrong with this side of things. BUT a gravity convection hw system should never have a valve in it as this is the safety heat dump for the boiler. (unless you also have a radiator that always gets warm even when only hw is selected...this is also a safety heat dump).
If you have a fully pumped system then it is likely that it is a control valve problem, can you identify weither a 3port or 2 port valve to switch between hw and ch?
hth
Ian L.
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Answers as follows :
Yes, central heating is working in all the ways you have suggested.
I don't know what type of circulation is in operation. However, I would suggest that it is gravity convection because it is an old system (old boiler), airlocks/bubbles are likely to be present (pipes are v. noisy & you can hear the water flowing in the pipes), however bleeding radiators has no effect on this. I don't know what happens when only HW is selected because we haven't lived there long enough to know. However, the radiator in the hall is the only one without a thermostat and remains hot when ambient temp. is high enough for other radiators to be off. According to previous owners the only way to run HW independently is to close one of the valves on one of the pipes in the airing cupboard.
In order to answer the rest I'll have to look at it when I get home.
Matthew Kelly
No, not that one.
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Just a couple of points, me not being a plumber
The wickes good ideas leaflet no. 50 gives a good overview of a central heating system; available online from their site if you don't mind registering :-(
I don't know when the 2/3 way valve to control the flow of hot water became common; but the system in my house (20 years old) doesn't have one, there is just a non-return valve to control flow to the rads.
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SpamCan61,
Sounds like you had gravity feed HW and a pumped CH system, the non-return valve is there to stop convection circulation into the radiator circuit.
Ian L.
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Matt
My thoughts
If your central heating is working OK, before condeming your zone valve (if you have one) try bleeding your HW primary circuit. You may have some air trapped in it.
The Primary circuit consists of the flow and return from your boiler to your HW cylinder. Inside your HW Cylinder is a coil made up of copper pipe, which when connected completes the primary circui. This basically works in exactly the same way as a radiator, only it heats the hot water in your tank, not in any room.
You should find a couple of bleed valves on the primary circuit near where the flow and return enter the hot water tank. You will need either a screwdriver, a small adjustable spanner or a key to undo them. You may be surprised at how little air is in the system, but expell this and you should be OK.
In case you have trouble locating the primary circuit. Look for a 22mm pipe that goes onto your cylinder part of the way up. On one side you will see a drain cock coming out of the bottom of the cylinder, with perhaps a 22mm cold water feed into into it (depending on the type of tank). That is NOT part of your primary circuit and should be left alone. Your primary circuit will almost certainly be the other side of this (180° opposite).
Hope this helps
Hugo
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Hugo
Thanks for that, v. interesting.
What I do have is a 22mm pipe that goes into the tank low down which has a valve attached similar to the valve one finds on radiators (not a thermostat one, the sort that you turn to isolate the water supply from that radiator, with typically a plastic cover on it to save you getting a tool to open/close it). I fiddled about with that last night and upon opening it water did start to drip out much like when bleeding a radiator, so I closed it again.
I think I need to get a good idea of exactly what pipework I have going into the tank so I can make the most of these suggestions.
Matthew Kelly
No, not that one.
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If it's right at the bottom of your HW cylinder, I suspect it will be a drain cock to enable you to drain off the cylinder, should you need to remove it for any reason. If I am right you should not need to touch that one.
Having just looked again at one of my cylinders (I'm currently in the process of connecting a primary circuit via a Zone Valve) I stand a little corrected on what I told you above.
On one side of the cylinder there will be two 22mm pipes, one near or at the bottom, the other will be about 1/2 way up. These are the connections to the coil (forming part of the primary circuit) that I spoke about earlier.
These at some point should each be T connected to probably 15mm pipes (but could be 22mm) which will go up and have a bleed valve locted at or around their highest points.
It is these you need to open and bleed.
Hope this helps
Hugo
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Yes I think you're right about my system ( non return valve is knackered, so I have to turn the upstairs rads. off manually in the summer :-( ). I was just trying to indictae to the original poster that they might not have a motorised valve anyway.
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Lots of ideas above but:
Do have a good look around your system and report back.
Then you will get good advice from the forum.
If you have a "gravity feed" system then you would normally have NO motorised valves in a normal sized house, just a pump. The pump is used just for CH. HW is by gravity. Hot water rises from boiler to the cylinder heat exchanger and cold drops back to boiler.
Can you normally select CH WITHOUT the HW operating?
If you try to operate CH does the controller also operate the HW switch?
The size of pipes going to the cylinder is not always indicative of the system type.
Have you altered anything or noticed any other symptoms prior to today?
We sorted out No Dosh by working our way through what he had and then systematically going through component at a time.
He had more than one problem and a lot of effort to sort it.
Even if you cannot sort it yourself, knowing the problem in detail, you will be in a stronger situation with the plumber / heating engineer. We await your replies.
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Description of the hot water tank and associated pipework (probably rather non standard).
There are four pipes exitting the tank, as follows.
Top of tank - one exit point leads in to a 90 degree junction, one pipe goes striaght up, the other eventually leads to the inlet for the shower pump.
Two thirds down, right hand side - 15mm pipe (well it's thinner than the other ones I take to be 22mm) leading to a radiator type thermostat valve. This has a rather antiquated (or so it seems to me) method of measuring the temp. of the cylinder. Attached to the valve by thin wire (like fuse wire) is a piece of copper tube which sits in what looks like an aluminium holder. This arrangement is held fast against the tank wall by some net curtain wire looped round the cylinder. This arrangement must be the prime candidate for failure I would think. Anyway after the thermostat valve the pipe continues to a junction with another pump which probably supplies the radiators - there is a pump above the junction and below it is a gate valve which we have been told by the previous owners of the house you have to close in order to turn off heating and run hot water independently. The radiator supply pipe also links to the radiator isolation type valve described in previous post, this valve leaks when turned to negative (closed?). The pipe emerging from the tank here is hot all the way to where it joins the tank, right from the junction to the radiator supply pipe, which I find odd, surely if the valve is not letting hot water into the tank it should be cold past the valve to the tank ?
Bottom left - 22mm cold pipe goes up towards loft - gate valve.
Bottom right - 15mm pipe - leads downstairs, there is a T junction which leads up to the radiator isolation valve described above at the top of about a 30cm run of pipe.
Hope this helps someone, I have a plumber booked for Thursday - but it would be good to be forearmed.
Thanks
Matthew Kelly
No, not that one.
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I assume your thermostatic valve has no electrical connections.
I had a similar installation on an old gravity fed system - it's a cheap alternative to a proper electrically driven motorised valve. The thermostatic valve started to stick in the closed position (so no hot water from taps). Fully opening then fully closing the valve would fix things for a few weeks, and then it would stick again.
It was replaced by a proper cylinder thermostat with a proper motorised valve (on-off operation only). Physically changing the thermostat and valve was no great problem, but it was tricky working out the correct electrical connections.
Strictly speaking, the system doesn't really need a valve at all, but if it is left in the fully open position the temperature of the water in the tank becomes too hot to safely put your hands under the hot tap.
Ian
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No electrical connections at all. I might go with the same again if it'll last a couple of years as the whole heating system will be comprehensively re-done when we have an extension built which we plan to do in a couple of years.
Matthew Kelly
No, not that one.
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I'll add that my original "thermostatic" system didn't use any type of cylinder thermostat. It worked only on the temperature of the water flowing through the pipe. You just adjusted the knob until the resulting hot water seemed OK.
Ian
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Top of tank - one exit point leads in to a 90 degree junction, one pipe goes striaght up, the other eventually leads to the inlet for the shower pump.
This is hot water out to taps and a vent pipe above your cold water tank in the loft. The vent pipe is an inverted U maybe 12 inches above the top of the tank Bottom left - 22mm cold pipe goes up towards loft - gate valve.
This is the cold water feed to the cylinder, for the hot water, from the big cold water tank in the loft
This gate valve shuts off the supply to all hot water taps / shower. Do make sure it functions. Shut it down and open it up every couple of months to stop it furring up. Do not have it fully open but shut it down about half a turn. This allows you to turn it in both directions if it does fur up. Bottom right - 15mm pipe - leads downstairs, there is a T junction which leads up to the radiator isolation valve described above at the top of about a 30cm run of pipe.
>>
This is the cold return from the cylinder heat exchanger back to the boiler
Hope this helps someone, I have a plumber booked for Thursday - but it would be good to be forearmed.
It certainly seems like an old fairly crude system.
Sorry I cannot advise you on a fix. It seems likely you have identified the problem as the cylinder stat.
It is normal to strap them on with what looks like net curtain plastic covered wire.
I hope spares are still available. If they are not, be prepared that your man may suggest putting in a couple of powered valves, an air/ room stat, a cylinder stat and a controller.
All these would stay when you update in the future but of course it would be a cost now. If this happens just ensure the valves are easily accessible so they can be changed and you avoid the No Dosh saga.
Good luck.
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Description of the hot water tank and associated pipework (probably rather non standard).
OK, I'll try and identify them for you Matt
There are four pipes exitting the tank, as follows. Top of tank - one exit point leads in to a 90 degree junction, one pipe goes striaght up, the other eventually leads to the inlet for the shower pump.
That sounds like it is your hot water supply, which will feed your power shower and your hot taps. The pipe that goes straight up will most likely go through your ceiling and act as an overflow into your header tank in the loft. This is essential incase the water gets too hot and literally boils over. If you don't have one of these there is a risk of your cylinder exploding.
Two thirds down, right hand side - 15mm pipe (well it's thinner than the other ones I take to be 22mm) leading to a radiator type thermostat valve.
This sounds like part of your primary circuit into your HW cylinder. Connected to this and the other pipe on the same side may be a bleed valve or screw. These are what you use to bleed the primary circuit as I explained earlier.
This has a rather antiquated (or so it seems to me) method of measuring the temp. of the cylinder. Attached to the valve by thin wire (like fuse wire) is a piece of copper tube which sits in what looks like an aluminium holder. This arrangement is held fast against the tank wall by some net curtain wire looped round the cylinder. This arrangement must be the prime candidate for failure I would think.
You have identified a closed loop feed back temp controller. The hotter the tank gets, the more the valve restricts the flow of water through the primary. This sounds like a thermocouple device, which I don't like in exposed permanent applications, although I have used these successfully several times in engineering experimentation.
Anyway after the thermostat valve the pipe continues to a junction with another pump which probably supplies the radiators - there is a pump above the junction and below it is a gate valve which we have been told by the previous owners of the house you have to close in order to turn off heating and run hot water independently.
This sounds like a low tech substitution for an electrically operated zone valve. This obviously stops flow to the rads so that the boiler is just supplying the cylinder.
The radiator supply pipe also links tothe radiator isolation type valve described in previous post, this valve leaks when turned to negative (closed?).
The pipe emerging from the tank here is hot all the way to where it joins the tank, right from the junction to the radiator supply pipe, which I find odd, surely if the valve is not letting hot water into the tank it should be cold past the valve to the tank ?
Sometimes a pipe can seem hot for a few feet. Copper conducts heat very easily and can "carry" heat beyond where water is stopped flowing. If the length of pipe we're talking about here is much longer or the heat is consistant (ie does not get colder as you feel towards the cylinder) then I would say that you have hot water in that pipe up to the cylinder.
Bottom left - 22mm cold pipe goes up towards loft - gate valve.
This is your feed from your header tank in the loft.
Bottom right - 15mm pipe - leads downstairs, there is a T junction which leads up to the radiator isolation valve described above at the top of about a 30cm run of pipe.
This is your return back to the boiler (other half of the primary circuit). This should also have a bleed screw near the cylinder. If it has, try bleeding it.
Hope this helps someone, I have a plumber booked for Thursday - but it would be good to be forearmed.
Others may wish to comment, but before spending money on a plumber I would try two things.
1 - bleed the primary circuit if you can, and see if their is any difference. Air in the system is the most common cause of many CH and HW problems.
2 - if that doesn't work or is not possible, see if you can remove the automatic dial from the radiator type valve that you describe above. You should be able to do this by unscewing it from the valve itself without actually removing the valve itself. Underneath you will find a small pin. The temperature sentitive dial pushes this in to varying degrees depending on the temperature. If you remove this dial, the pin will come up, effectively opening the valve to the full extent.
This way, if you have a blockage or an air lock, you may stand more chance of shifting it yourself.
Thanks Matthew Kelly No, not that one.
Let us know how you get on
Hugo
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Matt,
Sorry, missed the rest of the feedback yesterday evening....only have computer access at work.
Agree with the identification the others have given, looks like a gravity primary circuit for the HW and pump for the CH....however it is rather unusual in some respects.
For gravity HW it is normal to run 28mm pipes for the HW alone...so it is not affected by the CH pump. In your case 15mm pipe is really too small for gravity circulation and will be rather inefficient and much more susceptable to airlocks and silting up.
The thermostatic valve sounds like a standard radiator valve with external temperature sensor...not really designed for this mode of operation and its small aperture is not really suitable for gravity fed HW.
So if it is gravity fed HW then try removing any air from the system or removing the valve altogether.
Having said all that a number of things worry me....putting a valve in a gravity circulation is a bit naughty....reduces efficiency and might consistute a safety issue if you dont have a radiator on the HW side that always gets hot.
Can you confirm the location of the pump?
is it
1.
to middle of HW cyl
via thermostatic valve
________________________ to radiators via shutoff valve
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P
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from boiler
or is it
2.
to middle of HW cyl
via thermostatic valve
____________________P______ to radiators via valve
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from boiler
Case 2 would be gravity fed but extremely unusual and very inefficient (HW might only work when CH pump not on)
Case 1 would be fully pumped which might work but would indicate
either an airlock, silted up pipe or non-functioning thermostatic valve.
cheers
Ian L.
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Matt,
Just one more thought, the standard radiator thermostatic valves (with or without the external temperature probe) only last between 5 and 10 years before they require replacement as the actuating pin gets stuck due to lack of lubrication and acretion of limescale. Either Hugo or Henry said to remove the dial handle and you should see a shiny pin which is sprung loaded to force it out. Try pushing this pin in gently, if it is stuck in or out it will stop the valve working (stuck in will give you they failed hw symptoms). You can use pliers and some wd40 to try and release the pin and free it up.
regards
Ian L.
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Ian
Just got out of a meeting and the web access here is playing up a bit as well.
Location of pump - please see drawing below, you can judge which of your descriptions and little ASCII drawings best fits (if any, I\'m beginning to think we have some sort of bizarre mutation of a central heating system).
I
I
pump
I
thermostat I
cylinder ---rad. valve -----------------I
I
I
rad.valve-------I
I I
I I
I I
I I
I I
I I
I gate valve used
I to isolate rads.
I I
I I
I
I
I
from boiler
I
I
I
To remove the handle of the thermostatic valve, do I unscrew the whole vertical housing which has the dial at the top ? I started to do this last night to have a look inside but was worried about the possibility of getting scalding hot water everywhere, so stopped. There is a little screw at the bottom of the vertical housing, would removing this enable me to take the vertical housing off without water going everywhere ? I could then fiddle about with the pin as described.
Thanks for all your help.
Matthew Kelly
No, not that one.
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That's come out terribly - not like I did it in Notepad at all !
Looks like everyting is left justified and tabs don't work!
From left it should read tank, then horizontal pipe to thermostatic rad valve, more horizontal pipe to junction with pipe going vertically from boiler presumably to rads, pump above this junction, gate valve to isolate rads below junction.
Hope this helps.
Matthew Kelly
No, not that one.
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Matt, I have sorted it (I hope)
For info, if you want to include extra spacing or tabs, just as you would create itallics or bold text with the "> & <" marks surrounding them and also remembering to add "/" to turn it off, instead use the word "pre" (without the quotes).
DD.
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Thanks for that Dave, looks right now.
Matthew Kelly
No, not that one.
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Matt,
Not sure I understand your ascii art...the valve to cut off the radiators seems to be before the split to radiators and hw which would prevent both from working. I assume flow is from bottom of your figure to top?
As you mention I think you have a heavily adapted non-standard system which happened to work after a fashion but has now failed. It is probably not worth trying to debug the whole system here simple restore some hot water.
Even with a poorly designed/implemented system...it used to work so it should be possible to get it working again, the most likely culprit is the thermostatic valve. These normally have
a plastic handle which can be removed from the metal valve body
See www.mysoncontrols.co.uk/pages/trv.html for an example. Further down this page are details of capillary sensor versions (this is what I think you have). Does this look at all familar?
Ian L.
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I assumed that flow was from bottom to top as well, but as you say if you close gate valve it would cut off both HW & CH. Perhaps flow is from top to bottom.
The web address you've given doesn't work but I have found this, it looks like what I have (.pdf file from Google's cache of the Myson controls site) although the sensor in mine is far more basic and may be a cobbled together solution from a radiator valve and a bit of old copper rather than a specifically designed sensor which this one looks to have.
www.mysoncontrols.co.uk/pdfs/TCVDOC_1.PDF
I might try and dismantle it tonight. Would it be possible to do that without draining system / risking getting hot water everywhere ?
Thanks
Matthew Kelly
No, not that one.
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Inspired by the wealth of knowledge here, a question:
Our plumber has quoted for the replacement of the (3) tanks in our loft which he says are gently rusting away. His price, to replace them with plastic ones is around £700 including VAT. I have asked for a breakdown of the figure, but what do BRs think about the price?
By the way, access is difficult, and removal of the old tanks impossible, so they will be left up there.
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I'm a little surprised that removal is impossible unless they've been their since before the roof. I'd get them cut up and removed, if I was you. I am in the process of having mine removed this way.
I'd also check why you have three - seems a little strange. Perhaps one is a header tank, and another cold water, but I wonder what the third is.
On the other hand he's talking a little of £200 plus vat per tank, and whilst that is more than I'm paying for mine, its not greatly so. Although mine are pretty big.
Plastic is definitely better than metal.
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Agree, 3 tanks is a little odd, cutting them up is the usual method of removal since the originals are usually put there during construction or major renovation.
If access is really limited for installation of the new plastic tanks then two smaller ones can be doubled up to make the capacity of a single large cold water tank or you can get long thin tanks specially for this reason.
From screwfix the 50 and 4 gallon tank kits are 57.99 and 11.49
including VAT.
www.screwfix.com/app/sfd/cat/cat.jsp?cId=101561&ts...6
So how long is he estimating to do the job...a day is comfortable. So the plumbers time is expensive but not completely outrageous. But I would expect him/her to remove the old tank as well.
on the other hand if considering this myself I would convert to a sealed system and gain the space in the loft and the benefits of a pressurized HW system....but that is another story.
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Three galvanised tanks in your roof space?? Must have been there a long time. One must be your CH make up tank and as already stated the other two are presumably linked to enable them to be smaller and taken up through the trap door.
If the galv tanks have chalky patches on the outside dont touch these as they will be paper thin.
I wouldnt like the job of cutting them up in situ as an a disk cutter would have to be used as no one would want to use oxy/acetylene cutting galvanised in a roof space and I would find another way of removing them if required.
If you do replace the two linked ones ensure the plumber pipes them correctly. Cold feed in to one tank and all outlets at the other end of the second tank to ensure movement of water across the tanks and avoid stagnation.
£700.00 seems expensive to me and I like Ians idea of a sealed pressurised system.
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Fixed it last night by dismantling thermostatic radiator valve, pin was indeed stuck due to limescale. Chipped the limescale away and now it works fine (so far). As this was at about 10.30 last night I didn't cancel the plumber who came this morning and we had a general discussion about the system. He didn't seem that bothered about the way it was set up, not that he had a particularly close look, I think he was of the if it ain't broke don't fix it school of thought.
It's given me some food for thought for what to do when we replace the boiler when we bulid our extension. I'm not really sure who to turn to for reliable advice (other than the backroom!) but that's for another day.
Thanks for all your suggestions & help, much appreciated.
Matthew Kelly
No, not that one.
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Hi Matt
Glad you fixed it.
I suspect you'll be looking at a complete system overhaul when you have your extension built.
You don't live anywhere near the South West do you? I could recommend a good plumber.
If your house is going to be roughly 1200 square feet or less with the estension, you may like to think about a combi boiler, which would mean that your hot water is heated on demand when you need it. Most of your original plumbing could be left in situ, unless it needed changing anyway.
The drawbacks are:-
Hot water to upstairs can be a bit slow, takes longer to fill a bath.
Central heating pressure is typically 1.5 bar. 3 to 4 times that of a gravety fed pumped system, which can cause some weaker joints to fail.
Large houses are not suitable for this typr of system as getting hot water around it can be slow
Benefits
Lose that cylinder and all its bits from the cupboard
If your boiler is in or near the kitchen you'll get your hot water very quickly, as opposed to waiting for it to come down from a HW cylinder.
Our current abode (2,500 square feet) has a traditional pumped gravety fed system, and I have just fitted a 2nd HW cylinder to serve our new ensuite. The reason is that I want to be able to run two baths at the same time.
If you want to do some serous research, go to Wickes and B&Q superstore and read up on leaflets or even the B&Q diy manual. Also ask the staff in B&Q, superstore, they have qualified plumbers to advise.
Oh, and if you do end up doing it yourself:-
1 Get a CORGI registered plumber to install the boiler for you, and
2 Be vary wary of anything that promises to freeze pipes. My kit didn't work, which is why I am currently ringing out my clothes!
Hugo
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