lukewarm water from taps using vaillant 612 ecotech plus



Hello folks,

I am a new user and this is my first post. Am also not really technically minded.

I have a Vaillant 612 ecotech boiler installed. Was new 3 years ago and has worked perfectly until the last few weeks.

After I fitted in a new washing machine noticed that a few drops of water were leaking from bottom of boiler. Was advised that water pressure was too low. Released some water from nearest rad valve and pressure now correct and leak stopped. However since then water from taps does not get hot, only lukewarm. only heats up if the CH and water are on at the same time. If only hot water switched on the flame does not ignite although no error codes shown to reflect this. The CH works fine and heat up the rads. Only the water is lukewarm.

Any thoughts anyone pls. Have read similar posts here which mention heat exchanger, defective hot water thermister and stuck diverter valve :)
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Sounds like a faulty motor valve or control system.

You seem a bit confused about the pressure in the boiler. It needs to be set to about 1.3 Bar when system is cold.

Thanks for your reply Tony.

I adjusted the boiler pressure to now read between 1.2 and 1.5 Bar when the system is cold. Do you think that the loss of hot water was affected by the low pressure and the leak from the boiler (after fitting the w/m)? I don't exactly know why it was leaking but having read some online posts assumed it was condensation gathering.

Anyway the leak is now gone, pressure is ok but water is lukewarm. Me thinks I need to call someone in to have a look (and the boiler has not been serviced in 3 years).

If it is a faulty motor valve or control system I expect this will be fairly expensive to correct?

Thanks again.
Correction, the pressure reads between 1.5 to 1.8 Bar when cold!!
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Correction, the pressure reads between 1.5 to 1.8 Bar when cold!!

still to high really, get down to around 1.2 when cold, valves are not that expensive to replace as long as they are easy for the plumber to get at, say 1 hours labour + valve so about £160 + VAT
Hi Asif,

Sounds like external controls need checking, especially the control that is used for the cylinder temperature, which should be set at 60 deg c.
More likely to be the time clock is not heating water for long enough.

HW should be set to start 30 min before CH but to CONTINUE all the time the CH is on for. That includes evening times.

To reduce system pressure you can bleed a rad into a cloth.

Thanks for your input everyone. Will go through each suggestion one by one. Hope to have someone in to look at in after Xmas.

The thing I don't really understand is that the water from my taps is very hot after I have left the hot water on for a while. Kitchen tap and bath taps both very hot. However water from the shower is lukewarm. Do not the shower and tap water both get supplied from the same source (Santon Indirect Unvented Solar cylinder - which does heat up).

Will reduce the pressure. In the eves I do turn on the heating and water for 1-2 hours. All works correct except shower output is lukewarm. And boiler does not ignite when only set to water. Water and CH both need to be on for the burner to come on. Any ideas why burner would not fire when set only to Hot Water?

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