Two Water Heaters Don't Get Along

[benolit]

Hello. I am renovating a home that has two water heaters in two different areas of the house. "Heater A" is at the original location in the house, above the kitchen (house is on a slab, original heater location is in an large upstairs walk-in attic) "Heater B" was added in a back bedroom closet to (as the elderly previous owner told my realtor) make the bathroom water hot.

Here is the puzzle:
If shut off valves to both are open, then I get very lukewarm water everywhere.

If shut off valve to "Heater B" is closed and "Heater A" is open, then I get hot water in the kitchen (but not the bathrooms)

If shut off valve to "Heater B" is open and "Heater A" is closed, then I get hot water to the bathrooms (but not the kitchen).

Additional note that might help: the house has baseboard radiant hot-water heat warmed by a gas boiler, so the water has some connection there as well.

Any initial thoughts or ideas?

 

[johnjh2o]

It sounds like you have a cross connection between the hot and cold water lines. What type shower faucet do you have in the bathroom? Is it one or two handle? If it's single handle then the cartridge may need to be replaced. Of course it could also be that the heaters were piped wrong.

John

 

[plumbingjim17]

Could even be cross connection at boiler but John is right you are getting cold in hot line its mixing somewhere