Heating coming on with hot water but only on bath tap and shower

[jakeycrx85]

Hi

I thought I had a problem with my shower for a long time but now I've realised it's something to do with the boiler or possibly the pipework.

I have a Valliant Ecotec plus 824 VUW GB 246/3-5 located in the kitchen. The kitchen tap which is right next to the boiler supplies hot water with no problems. The tap on the bathroom sink supplies hot water with no problems. The bathroom tap is almost directly above the boiler.

The bath tap and separate shower are the problem. They are the furthest away from boiler. The water is only warm from the bath tap and shower and the hot water is diverting into the central heating system. From what I have read the diverter valve seems the likely culprit but why does it only do it on the bath tap and shower? Could extra back pressure from a longer pipe run cause a tired valve to unseat compared to the shorter pipe runs of the kitchen sink and bathroom sink where it stays seated?

I also noticed I have no temp control on the hot water when running the bath tap and shower. With the kitchen and bathroom sink hot tap running when I adjust the hot water temp on the boiler it goes up and down as it should but when i adjust the temp with the bath tap or shower on it just floats around 61-63 degrees no matter what I set the hot water temp to. I've also noticed I lose pressure from the central heating system and sometimes it gains pressure and goes too high.

One other thing worth mentioning is I had the bathroom completely redone about 9 months ago and everything was moved around so a lot of the pipework has been changed. Is it possible the bathroom fitter has messed up the pipework that runs to the bath? The flow rate seems OK from the bath tap and shower though. I think the shower is fed off the old 21/22mm pipe that used to go to old immersion tank in the airing cupboard. I got rid of the airing cupboard to expand the bathroom.

My shower is a thermostatic Grohe and it has been playing up for a while now (not getting hot enough) so I can't quite remember if it started happening after the bathroom was done. In the past I've removed the shower body and filled it full of Viakal and left it for a few hours and that sorted it out.

 

[AGAS]

if i read it right . if your heating gets heat while running hot tap you need rgi to fix also what your reading on screen regarding hot water temp is the temp of heating system

 

[jakeycrx85]

if i read it right . if your heating gets heat while running hot tap you need rgi to fix also what your reading on screen regarding hot water temp is the temp of heating system

Yes. The central heating warms up with the hot water on but only on the bath tap and shower and the water is just warm, not hot. When I run the kitchen tap and tap on the bathroom sink the central heating does not warm up and I get properly hot water. What is RGI?

 

[Dan Robinson]

Registered gas installer.

To fix this means taking the front of the boiler off.

Less than an hours work to fix this once the parts have been sourced.

 

[jakeycrx85]

Why does it only do it on the bath tap and shower though? The kitchen tap and bathroom sink tap have no problems.

 

[DP]

Why does it only do it on the bath tap and shower though? The kitchen tap and bathroom sink tap have no problems.

Because kitchen tap and bathroom sink (I think you mean basin) are sporadic use, but bath and shower use results in sufficient leaked primary water to be in the radiators to highlight the malfunction

 

[jakeycrx85]

Why does it only do it on the bath tap and shower though? The kitchen tap and bathroom sink tap have no problems.

Because kitchen tap and bathroom sink (I think you mean basin) are sporadic use, but bath and shower use results in sufficient leaked primary water to be in the radiators to highlight the malfunction

I call it a sink. During my testing I have left the kitchen tap and bathroom sink tap running for long periods of time and the DHW does not divert into the CH. Also the water from the bath/shower is only ever warm it is never hot. The kitchen/bathroom sink water is always hot and remains hot.