Troubleshooting - No Hot Water with Kohler Universal Valve

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Liam313

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Hello,

I have a Kohler single-handle universal valve (K8304-K-NA) installed on a recent renovation. It was working properly when installed, but after several months no hot water flows when turned on (gradually got worse). I am trying to troubleshoot what the source of the problem is and what potential solution could be implemented.
  • I have tried two replacements of the same model (one from local seller, one from Kohler) and the problem persists. When the cartridge isn't installed hot water flows fine. When installed no hot water.
  • Testing the hot and cold psi in the sink next to the tub, both are at 35psi. I installed a pressure regulator on the hot water line and it also shows 35psi
  • Recommended psi for this model is 45psi but has a range of 20-125psi, with no difference between hot and cold greater than 5psi
  • The hot water does not flow regardless of using tub filler vs. shower head. The water heater is an electric on demand water heater.
My best assumptions moving forward are to install a pump to increase the water pressure (bathroom located on 3rd floor). Any recommendations? Or install a pressure regulator on the cold line as well to test reducing psi on either to see if that works. Are there any other recommendations on troubleshooting steps or solutions to this issue? I've reached out to other local plumbers, the local parts store, and Kohler engineers and haven't been able to resolve this.
 

Dj2

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" It was working properly when installed, but after several months no hot water flows when turned on (gradually got worse). "

" When the cartridge isn't installed hot water flows fine. When installed no hot water. "

- 35 psi in the sink next door is a bit too low. You want 50.
What is the pressure coming into the house?
Why did you install a PRV on the hot line?
 

Liam313

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- What is the best method for increasing the pressure to the 3rd floor?

- pressure coming into the house is 50psi. there is 3/4 pex going from basement straight to 3rd floor where 1/2 pex splits to 3rd floor fixtures and on demand electric water heater (also located on 3rd floor, 1/2 in and out). 3rd floor is roughly 35 feet off the ground so 15psi drop is expected.
- I installed the prv on the hot line to see if adjusting hot water pressure would solve the problem. it did not, so it is currently completely open. I can remove it or see if it is needed once overall pressure is increased. But I'm not sure what the best method for increasing pressure is.
 

breplum

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I am suspecting that it is a pressure balance issue related to the low pressure.
Surprised that Kohler tech support is not able to help.
PRVs are not called for so remove them for sure.
What is your supply line size? It is all pretty weird. You have good hot water flow at the sink...and water flows fine w/o the valve, so it is the valve.
The K304 is an old workhorse, but it IS the problem here. Pressure balancing unit for sure.
 

Jeff H Young

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you got water in 35 psi both sides no water out , I suppose its not impossible to be something else but obvious to me as well pressure balancer or something else with cartridge.
 

Liam313

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I am suspecting that it is a pressure balance issue related to the low pressure.
Surprised that Kohler tech support is not able to help.
PRVs are not called for so remove them for sure.
What is your supply line size? It is all pretty weird. You have good hot water flow at the sink...and water flows fine w/o the valve, so it is the valve.
The K304 is an old workhorse, but it IS the problem here. Pressure balancing unit for sure.

My first guess was faulty cartridge, but Kohler sent a replacement and I also tried a replacement from the store. All three cartridges result in the same issue which is why I'm having trouble finding out what the problem is. Kohler tech and other plumbers who have inspected can't seem to identify what the problem is. What is even harder to understand is why it was fine when initially installed and got worse over time.

All the fixtures have 1/2 supply for hot and cold. My only remaining ideas are increase the water pressure to the optimal 50psi recommended (which I could use advice or recommendations on parts) or switch to two handle hot and cold (which is not ideal for many reasons).
 

Jeff H Young

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changed entire cartridge including the pressure balance spool? you need to go back through a nd check it all out your missing something very simple
 
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