Hi there,
We've got a problem that I'm hoping someone has some thoughts on. We have a Grohe thermostatic bath/shower mixer in a first-floor bathroom which is fed by a combination boiler. The intsallation has worked fine for around 8 years without problem.
Around 2 months ago the hot water in the shower started to fluctuate between hot and cold - no regulation at all. Eventually, it got tot the point where the water was more cold than hot. At the time this seemed to be straightforward issue and an I replaced the thermostat cartridge in the mixer body. Unfortunately, the problem remained - though it did seem that the water was generally hotter than before but still fluctuating between hot and cold.
At this point I investigated in more depth - I should have done this the first time around!. The hot water in the kitchen, i.e. adjacent to the boiler was constantly hot when measured at the kitchen mixer tap. In the bathroom, the hot water at the wash hand basin was constantly very hot - all seemed good. I take this to mean that there is no issue at the boiler.
With the bath water turned on and the thermostat mixer set to maximum heat then the bath flow was fluctuating between hot and cold.
However, if the cold water in the wash hand basin is turned on then the bath/shower water is warm/hot, i.e. hotter than before but still not regulated. With the wash hand basin cold water turned off then the bath water returns to fluctuating hol/cold water. It seemed to me that this pointed to the non-return valve on the hot water not operating correctly so allowing cold water to feed into the cold water, however, one new non-return valve later the problem remains. This seemed a long shot given that both the cold water and hot water are mains pressure so I didn't think that the hot water would generally be able to feed back into the cold feed.
I'm now stumped as I do not know where else to look - does anyone have any ideas?
We've got a problem that I'm hoping someone has some thoughts on. We have a Grohe thermostatic bath/shower mixer in a first-floor bathroom which is fed by a combination boiler. The intsallation has worked fine for around 8 years without problem.
Around 2 months ago the hot water in the shower started to fluctuate between hot and cold - no regulation at all. Eventually, it got tot the point where the water was more cold than hot. At the time this seemed to be straightforward issue and an I replaced the thermostat cartridge in the mixer body. Unfortunately, the problem remained - though it did seem that the water was generally hotter than before but still fluctuating between hot and cold.
At this point I investigated in more depth - I should have done this the first time around!. The hot water in the kitchen, i.e. adjacent to the boiler was constantly hot when measured at the kitchen mixer tap. In the bathroom, the hot water at the wash hand basin was constantly very hot - all seemed good. I take this to mean that there is no issue at the boiler.
With the bath water turned on and the thermostat mixer set to maximum heat then the bath flow was fluctuating between hot and cold.
However, if the cold water in the wash hand basin is turned on then the bath/shower water is warm/hot, i.e. hotter than before but still not regulated. With the wash hand basin cold water turned off then the bath water returns to fluctuating hol/cold water. It seemed to me that this pointed to the non-return valve on the hot water not operating correctly so allowing cold water to feed into the cold water, however, one new non-return valve later the problem remains. This seemed a long shot given that both the cold water and hot water are mains pressure so I didn't think that the hot water would generally be able to feed back into the cold feed.
I'm now stumped as I do not know where else to look - does anyone have any ideas?
