Water Heater Bypass Question

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Oct 9, 2018
Hello everyone,

First time post - we just purchased a very lightly used (2 or 3 trips) 2018 Springdale 3030BH travel trailer.  It's new to us so a forum like this is so valuable since I prefer to do maintenance myself.  We're going to be winterizing it this weekend.  My question is in regards to the water heater bypass line.

I've attached a picture so you can see what I'm looking at, but why question is this:  I believe the bypass line valve is at the bottom there on the cold water line, but there doesn't appear to be any other valve up at the hot water "exit" line.  If I activate that bypass valve and use the bypass line that's running vertically, what keeps the antifreeze from running up that bypass line and then into the water heater through the hot water line at the top of the unit?  Is there some sort of backflow preventer or something in that line that makes it "exit only" and keeps liquid from running back into the water heater when the bypass is activated?  Thank you very much for your help


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Well-known member
Oct 4, 2007

There is usually a check valve in the hot side of the heater output that will prevent the flow of Antifreeze going back into the heater by the back door.

Rene T

Site Team
May 20, 2011
Farmington NH
What Stu said. If you look real close at the hot water line, the fitting which screws into the tank is a little different than the bottom fitting because it is a check valve or at least it should be.  Some time in the future if you find that you've lost water flow to all the hot faucets, it will probably be this check valve. it's very common for them to fail and stop the flow of hot water. If you're in a area where there is no need to ever winterize, just remove the check valve, know out the internals then reinstall. Or for a temporary fix until you get a new one. They can be purchased at many box/hardware stores.
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