Hot Water Even With Cold Valve Fully Open

[Jaroob]

Hello all,

I am new here so I don't know if this is the best forum thread to post this, so just point me in the right direction if that happens to be the case.

My situation is this though. I just installed a new tankless water heater in my home after the old tank style finally bit the dust. In doing so, I also added a recirculation pump to the hot line of the water heater to alleviate long wait times since my showers are one of the farthest things from the heater. There is no dedicated return line in my home so I have installed a crossover valve under one of the bathroom sinks. Everything works as it should with the recirculating pump EXCEPT for both showers/bath in my home.

This is the weird part though. Both showers are 2 valve systems (separate hot and cold valves). If I turn on the hot water valve first in either shower, and then turn the cold valve on, it just stays ridiculously hot with no control over water temp, even when I fully open the cold water valve and have the hot water valve maybe a quarter of the way open. However, if you turn the cold valve on first or shut the hot water valve off and turn it back on, I have much more control over the water temperature coming out of the shower head.

I know it has something to do with the recirc pump as when I turn it off, the showers have no problems at all with temperature control. My question is, why is that happening and is there a way to fix it?

Thanks!

 

[Jeff H Young]

A dedicated return line be a good fix

 

[Sponsor]

 

[Jaroob]

A dedicated return line be a good fix

This may be true, however, I forgot to mention all my current piping goes through a concrete slab. While it still could be done, I'm sure there must be a more cost effective way of fixing the problem. I'm fine with a little bit of hot water creepage in the cold lines, but the showers will constantly just stay hot.

 

[Jeff H Young]

Any chance the crossover valve under your lav is bad? Perhaps get rid of the old shower valves

 

[Jaroob]

Any chance the crossover valve under your lav is bad? Perhaps get rid of the old shower valves

The crossover valve is brand new. But, that doesn't necessarily mean it's not bad either. I can check it out more to see if that might be the case.

I thought about a new shower valve with a mixing cartridge instead of dual valves. Would the mixing cartridge prevent hot water from over powering the cold water? I know most today have pressure regulation when mixing to ensure proper mixture. Do you think that would solve the issue?

Thanks

 

[Jeff H Young]

I guess put your hand on that cross over if its hot and not warm on cold side its not working right should be troubleshooting info on it.
Thermostatic would be even better but pressure balancing usually work great . something is wrong beside your old shower valves if this problem never existed before

 

[Jaroob]

I guess put your hand on that cross over if its hot and not warm on cold side its not working right should be troubleshooting info on it.
Thermostatic would be even better but pressure balancing usually work great . something is wrong beside your old shower valves if this problem never existed before

It seems to be working if doing what you said confirms it. Also, one thing to mention is the water heater does run consistently every now and again and then shuts off when nothing else is on. I would have to assume thus means the valve opened properly and then closed once the water reached a certain temperature causing the water heater to stop heating water.

Yes, when I shut the recirc pump off though, the showers works as they previously did before with my tank water heater. I just don't know why it's only affecting the showers when it on because all of my faucets in the house are fine.