If you have a 1 or 2 valve system with check valve... ANd the check valve has failed (There are two failure modes) Then .. It will not check.
The two failure modes.... (And one can lead to the other)
1: The valve "limes up" with mineral deposits and will not open, this leaves you taking one COLD shower, cause there is no hot...
Now one way of fixing this is to "Gut" the valve.. do that and you now get full hot flow.. but the check valve now works as in 2:
2: Stuck open, allowing back flow.
Suggestion: Winterize by the DRY method.. For now, that means open all vavles, Low point, Faucets, everything, and get an air compressor (portable) with regulated output, set to 50 psi and blow till nothing more comes out.. Have a cup of coffee.. Blow again, and again, (Like 10 times with about 3-5 minutes between blows) shut it down.
If the air thus left in the lines ever freezes... You won't care.. Neither will I, (If air freezes breathing becomes... Impossible).
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times