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pokipaul 01-03-2013 11:18 PM

Low Hot Water Pressure Tub Only - Single Control Valve - Thermostatic Mixer
I have a Shower / Tub Combo. Shower and Tub both have a single Hansgrohe Volume Control Valve each. There is a Ecostat Thermostatic Mixer for controlling the temp on both values, all supplied by a thankless water heater.

The shower pressure is fine.
The tub (which we have not used in a while) - Cold water comes out in large volume. When the water temp on the mixer is set to hot, the water output drops to a very low level.

Bathroom and Kitchen faucets are all fine.

I have read that replacing the cartridge seems to be a common fix but if I have a single Volume control valve, why would the cold water be fine?

Is there a replaceable part in the Mixer?

any help thanks..

Ishmael 01-04-2013 06:21 PM

I think we're all generally stumped on this one as you've described it. Each outlet has its own volume control, and there's one thermostatic valve feeding both. The shower head is fine, and the cold water is fine at the tub. But the hot water at the tub is weak?!?


My only guess at this point is that the shower head has flow restrictors that make the problem virtually unnoticeable there. But the tub spout is full flow, so when you advance all the way to max hot, the drop off is obvious. If that's the case, you'd most likely have to replace the cartridge - although - Grohe valves tend to have lots of screens inside; you may pull out the cartridge and find "stuff" clogging the screens on the hot side?

pokipaul 01-04-2013 06:59 PM

1 Attachment(s)
Thanks for the reply, here is my layout.

I will pull out the cartridge in the Temp Control Mixer and see..... my not so wonderful contractor grouted my escutcheon plate so I have to chisel that carefully off:mad:

any tips on how best to remove the grout?


pokipaul 01-05-2013 06:26 PM

1 Attachment(s)

Took out the Cartridge from the mixer and it was packed!!!
Cleaned out and all is back to normal.


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