Sporadic hot water - Only some fittings getting hot water

[sterennie]

Hi everyone,

I am having some trouble with the hot water supply in my flat and any advice would be appreciated! My knowledge is fairly limited on this sort of thing but I will try and explain as best I can.

We have an all electric flat fitted with a mains direct unvented hot water cylinder, heated by immersion. We have been turning on the immersion as and when we need hot water so far (moved in about 5 months ago) and while this is a slight pain it has been working ok.

There is also a switch for a pump (circulation pump I guess??) in the cupboard that houses the cyclinder, and we have never used this. The hot water would take a couple minutes to come through to the ensuite bathroom and shower as well as the kitchen sink, but that didnt bother us.

However, about a week ago we suddenly started to not get any hot water through to the ensuite bathroom and the kitchen sink, even after running taps for a long time. The strange thing is though that hot water is still coming out of the other bathroom shower and sink which happens to be immediately adjacent to the cupboard housing the hot water cyclinder. So we are now having to use this for our showers. Also, the hot water comes out fairly quickly unlike other places in the flat, and always has done - I guess as its so close to the hot water cylinder?

Any ideas for possible reasons for this to be happening? Ive tried googling and initially thought there may have been a problem with the shower bar valve thing, but that wouldnt explain the lack of hot water to the ensuite sink and the kitchen sink.

Cheers

 

[plumberdan]

What colour is the pump? The speed the water leaves the taps can be down to the type of tap! The smaller the hole(spout) the faster the water appears to flow, like nipping the end of a hose pipe! The hot tap on the bath should have the most water as the pipe to it is bigger than the other hot and colds! Is it economy 7 electric, cheap on the night and expensive during the day?

 

[flameport]

Some possibilities:

Pump is there due to the excessive distance between taps and cylinder, and has got blocked /seized due to not being used, and is therefore restricting the flow to the affected taps.

Dual immersion heaters, the lower element has failed, and the affected taps are connected to a lower point on the cylinder which is now always cold. The other taps connect at the top where the hot water is.

The pumps is actually part of some heat exchanger circuit, and that has become blocked for whatever reasons.

 

[picasso]

stuck non return valve either on the kitchen sink, shower or anywhere the hot and cold "meet", depending on how your flat is piped up will affect which hot outlets are running cold, could even be the non return valve on the secondary pump. (the one your not using)

 

[plumberdan]

Both of the above are very incorrect, the hot water leaves the cylinder from the top or top side not bottom, the pump is a secondary circulation pump that does not cause adverse affects if blocked removed or turned of! does allow hot water to reach taps faster if in operation! There should be no check valves fitted as that would cause problems, all pressures should be balanced ruling out the need for check valves! Havnt got a solution yet myself!

 

[picasso]

Both of the above are very incorrect, the hot water leaves the cylinder from the top or top side not bottom, the pump is a secondary circulation pump that does not cause adverse affects if blocked removed or turned of! does allow hot water to reach taps faster if in operation! There should be no check valves fitted as that would cause problems, all pressures should be balanced ruling out the need for check valves! Havnt got a solution yet myself!

You havent fitted too many secondary circulators I take it, if the kitchen tap is taken off before the cold water controls the pressure can be a lot higher than the hot pressure so you would fit a nrv on the hot.

 

[sterennie]

Just to confirm, the pump that I mentioned is a Terrier TC6 circulating pump. As I said, I dont know much about this kind of thing, but I figured this would be used to ensure hot water is fairly instant at all taps/showers etc.

Also just to clarify, all taps and showers are mixer units, so only have one spout for both hot and cold water, and the water pressure is consistent and good at every tap no matter whether turned to the hot or cold position.

We dont have economy 7 tariff, and we do indeed have dual immersion heaters (we only ever use the half tank one) and both are working as normal.

 

[plumberdan]

Yes sorry there's a requirement for a check valve near the pump to prevent back flow, but any qualified fitter of unvented cylinders should know to balanced out the cold mains to the house, cutting out check valves on taps showers etc. Even if the check valve next to the pump had jammed there should still be plenty of water to the taps(Hot water) it would just take a while to get there!

 

[picasso]

The terrier TC6 is only suitable for heating systems, you should have a bronze pump if its on the hot water system, if they have installed the wrong pump there is a good chance they have not installed a nrv either which would give the problems your getting now.

 

[plumberdan]

That pump will just rust up and jam anyway! The system has been operating correctly for 4months so the lack of check valve next to pump can't be it otherwise it wouldn't have worked when they moved in! I suggest you get a BPEC domestic hot water storage systems qualified installer to check it over because it sounds like you have a few small problems regarding the installation of the unvented cylinder, if installed incorrectly theses things can cause explosions and level houses! It would be difficult to install one that badly though!

 

[sterennie]

Oh, I see. So the blue terrier pump has nothing to do with the hot water supply?

I am at work right now so will have to check about the bronze pump a bit later. But if there was one, would this also be powered by a switch? Because the only switches in the cupboard are the immersion on/off, immersion bath/sink, and terrier pump switch.

We havent altered anything since we moved in, so that pump has always been there and there was hot water available to all taps up until a week ago.

Do I need to check any of these no return valves when I get home? Im not really sure what they are..

Also, I dont know if this is useful information, but the flat has underfloor heating throughout, although we havent used this yet as there has been no need.

Thanks for all the replies so far.

 

[picasso]

Can you post the name and model of the hot water cylinder ?

 

[plumberdan]

A few pictures of the cupboard would help us identify your system better! You can't see if the check valve/non return valves are working correctly the components are internal! The pump may well be part of the heating system, as for the immersion switches its sometimes cheaper to just leave them on depending on user requirements for hot water! Try leaving them on tonight and try the taps in question tomorrow!

 

[sterennie]

Ok, so the hot water cylinder is a Ultrasteel direct mains pressure stainless steel 150 litre tank. Here are some pictures of what is in the cupboard:

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• sterennie
• 22 Aug 2011
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• sterennie
• 22 Aug 2011
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• sterennie
• 22 Aug 2011
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• sterennie
• 22 Aug 2011
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If you want any other/better pics let me know. Thanks again for the help.

 

[picasso]

you have the wrong type of pump installed, the terrier is for heating systems and will quickly rust away, if your not going to use it, close the valves either side and see if that stops the hot taps running cold, if it does that proves that the nrv (just under the pump) is stuck open,

if it doesnt solve the problem I would leave the pump isolated until your ready to change it, then its a case of isolating each outlet until you find the one that is passing cold water into the hot supply.