Domestic Hot Water

[rwalters]

We have recently moved into a new house and have a problem with the domestic hot water. We have a vaillant combi boiler (do not know the exact model), central heating is fine and domestic hot water downstairs seems to be fine. The bath and shower upstairs sometimes fails to light the bioler. The bioler clicks and click as you can hear it trying to light but it does not fire. We have to turn the hot water tap or shower off and try again, after a couple of attempts it will eventually fire and give hot water. The shower is more of a problem than the bath, but I am presuming this is because the water pressure through the shower head will be less. Also, if you can finally get the hot water running and get into the shower, sometimes it will go cold on you again (not very nice at 6 in the morning).

We have a BG contract and they can out a couple of weeks ago to replace a leaking pressure valve and we mentioned this to him and his said in some houses and certain boilers it is normal as the water pressure is not high enough. If this is the case, is there anything that we can do?

Many thanks in advance.

Richard

 

[ChrisR]

Yes it's true but the boiler may be starting to go wrong. Diverter Valve senses the water flow using a perishable rubber diaphragm. Meanwhile try turning the basin tap on a bit while you're showering. Some taps turn themselves off of course...
I bet your water main is hopelessly undersized and shared with other flats?

With CH OFF turn a HW tap on. If the leftmost pipe (fat one) under the boiler gets warm your DV is faulty.

 

[rwalters]

Thanks Chris for your reply, we live in a detached house, and the mains water pressure is fine as the water from the cold water taps comes out extremely fast, so i don't believe the problem lies with the actual water supply, but rather with the boiler itself.

Could you explain to me what the diverter valve does, is it easy to locate and is it easy/expensive to replace.

It is a strange problem, this morning the shower was fine, not a problem at all, but I bet tomorrow it will have a problem, which leads me to believe it is the boiler.

Thanks again Chris for your reply.

 

[ChrisR]

Sorry I thought I was answering someone who was in a flat!
As you haven't told me what your boiler is it's difficult to tell you where to look for the diverter valve!

With all but the current vaillants there's a device with a rubber diaphragm which is used to detect water flow. When the rubber gets tired , or the bits it pushes stick, you need more flow to get the job done. So if the shower flow is less than the tap flow the result will be worse.

The water going cold once started flowing hot, is likely to be due to sludge in the HW heat exchanger. Boiler can't get energy through a sludgy h/e so it turns the flames off. Diagnosis calls for temperature probes inside boiler. BG don't cover sludge - it'll need desludging and/or a new HWHE.

I have already described how to test if the DV is faulty.