Shower mixing valves

[Splinters]

I have 2 Showers aboard our boat that are not providing enough cold water during operation. No matter which cold setting you put it on the water comes out very hot. I suspect this does not have to do with the mixing valves on both units because this just started happening after commissioning the boat this Spring. Any advice would be appreciated. Thank you in advance.

[chris95040]

Diagram your plumbing and consider ways hot water could be pushing its way into the cold water loop.

Remember PV=somethingsomethingT, your hot water tank gets pressurized as it heats up.

Maybe a check valve in the cold water feed to your hot water tank has failed.

[Splinters]

Thank you for the quick response Chris! I have heard a lot of clicking sounds coming from the check valve outside the hot water tank, I suspect that you may be correct, I will empty tank and remove the exterior check valve to inspect.
Thank you again!

[Lepke]

The type of check valve and how it was installed makes a difference. If you use a metal valve with a swinging disk, it's best if the valve is orientated so gravity closes the disk. Otherwise use a valve that is closed by a weak spring.
A warming water heater doesn't suddenly create pressure. So the backward flow is gentle. A metal check valve installed so the disk is normally open, won't react to a very low flow.

[Splinters]

Lepke,
Thank you for the advice. I installed the check valve 6 years a go so Im very familiar with the unit. That said I will disassemble and see if it has a spring seeing that I installed it horizontally. If not, I may orient it upwards so that it closes due to gravity.
Many thanks!
JP

[flightlead404]

Originally Posted by chris95040

Remember PV=somethingsomethingT, your hot water tank gets pressurized as it heats up.

Its "PAV - NURT".

https://xkcd.com/2492/