# Hans Grohe Pressure Balance problem



## Scott K (Oct 12, 2008)

Was doing some odds & ends heating work for a new construction project (some boiler stuff) and the house is near finished and the homeowners live in the house now. They have a shower with 2 shower set ups (husband/wife) and 2 toilets (big master bathroom). So they have his & hers toilets & his & hers shower but the shower is common for them (nice set up!). They each have their own Hans Grohe Showerhead, thermostatic valve, & on/off flow control valve. 

Their complaint is sometimes when one of them flushes the toilet while the other is in the shower one of the showers will go hot, or one will go cold.

I tried to replicate the problem. I didn't get it going hot, or going cold, but it did start doing this strange oscillating thing where it would fluctuate from slightly hotter to slightly colder, back & forth every half second say. 
I pulled it apart and the strainers before the check valves on the integral stops (big allen key) looked clean although there was a micro sliver of teflon but relative to the surface area shouldn`t have made a difference. 

I talked to the guys who did the water line installation and by the sounds of it, there shouldn`t be any flow issues, but that shouldnt`matter with a pressure balanced system anyways; if a toilet flushes, the pressure drops on both hot & cold anyways.

Any insight is appreciated for this not much of a service plumber yet (more of a new construction & hydronic heating guy).


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## plumbpro (Mar 10, 2010)

Scott K said:


> Was doing some odds & ends heating work for a new construction project (some boiler stuff) and the house is near finished and the homeowners live in the house now. They have a shower with 2 shower set ups (husband/wife) and 2 toilets (big master bathroom). So they have his & hers toilets & his & hers shower but the shower is common for them (nice set up!). They each have their own Hans Grohe Showerhead, thermostatic valve, & on/off flow control valve.
> 
> Their complaint is sometimes when one of them flushes the toilet while the other is in the shower one of the showers will go hot, or one will go cold.
> 
> ...


I don't know about Grohe, but on a delta pressure balance the pressure will drop on both sides when another faucet is open. If you are losing pressure on one side and not the other, I would think that would be a defect with the cartridge?? not sure. Are you sure the water lines are sized properly?


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## stillaround (Mar 11, 2009)

I have had to change a thermostatic cartridge before...warranty and Grohe was nice. I have Grohe and it never happens to me in my house...just a thought..you know how to set the temp dont you. Some have a small stop thats supposed to be at a 100 degrees and then you can force it hotter. If the adjustment is way off maybe it could cause a malfunction. You can remove the handle and then turn the nut and reinstall.


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## Optimus Primer (May 20, 2009)

There is a spool inside the cartridge. Sometimes that sticks. All I ever had to do was take it out of the valve and shake it or twist it where the joint is and it worked fine after that. Could be some debri holding it open or something like that.


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## stillaround (Mar 11, 2009)

Thats right...forgot bout that.


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## 1plumb4uall (Jan 6, 2010)

The first muti head shower I installed was a Kohler set up and they had the same probem, so I call up MR Kohler the said I needed a PSI reducing valve on H & C no more than 50 lbs .................. hey it worked.


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