Hansgrohe Thermostatic Valve Pulsing
I just installed a Hansgrohe Thermobalance I in a new shower. Everything works fine when the temperature is set to either the hot or cold ends of the spectrum. The problem is when it is set some where in the middle ... you know ... where people actually like to shower. The water flow pulses pretty badly in this range. It seems to me that the valve is constantly trying to adjust the temperature and overshooting, almost like a drunk trying to keep his wheels between the dotted lines. Is this a common problem with thermostatic valves? Could it be a problem in the supply lines somewhere?
Possible solution to problem
Your cartridge has filter screens to catch dirt particles and protect the thermostatic element. If you used bread to make your tie in, the screens are probably clogged. The solution is as follows. Remove the trim plate and handle. If you have one of the ThermoBalance valve models, you need to hold the wrench flats steady (They are positioned at 9 and 3 o'clock) then remove the 94282000 cartridge by turning the large hex nut counter clockwise while holding the wrench flats at 9 & 3 o'clock. Once removed clean the filter screens. Before replacing, you should turn the barrel of the cartridge counter clockwise (water should be on) about 1/4 turn to clear any debri left in the valve. Reinstall the 94282000 cartridge into the unit and reinstall the trim. The handle will need to be recalibrated. You should find the instruction manual for the directions.
If you have the Ecostat or EcoMax valve, you must turn the water off at the service stops first. Then remove the center thermostatic cartridge and clean. Cycle the service stops to confirm strong flow and flush the valve before replacing the thermostatic cartridge.
Thermostatic valves are wonderful and can supply alot of mixed water for larger demand. Hansgrohe tests 100% each cartridge before it ships to you, so you should never get a lemon. Best shower product on the market in my opinion.
If you have the same problem after cleaning and flushing your valve, the other reason can be an undersized instant water heater. Thermostatic valves cannot cope well with differing pressure between hot and cold. Instant water heaters can reduce the pressure on the hot side too much for the valve if it is undersized.
Also, Hansgrohe has a knowledgeable technical service department. If you need more support, contact them at 800-334-0455 from 8:00 to 6:00 M-F