1 valve system would be a 3-way valve
Turn handle parallel with cold water line and water goes into WH Tank
Turn handle 90* so it is perpendicular with cold water line and water 'bypasses' WH tank. Goes to hot water line and then hot water plumbing. Check valve in Hot outlet stops back-flow into WH Tank
2 valve system.......
Have to CLOSE cold water inlet to WH Tank
Have to OPEN bypass valve
Check valve on hot outlet stops back-flow into WH Tank
Problem...
Incorrect valving
Bad valve
Bad check valve
Disconnect cole water inlet at water heater to check for bad valve
If valving correct then most likely bad check valve in hot out
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31