Winterizing Mystery

[Ed4000]

Hi guys, I fouled up while winterizing yesterday, and can't figure this out! 
2016 Keystone Passport TT. I drained water heater and low point water drains & fresh water tank, then turned water heater bypass valve. I then put the antifreeze to the pump to start pushing it to the faucets. HOWEVER , and this is where I think I really messed up, I forgot when draining to open up the faucets to release pressure and let the lines drain back from the faucets. So what happened is that when I began pushing the antifreeze with the pump and started opening up faucets,  I was getting weak flow. I happened to stop and go back outside and found pink water running out of previously drained water heater.  I verified that water heater bypass was on, so I'm stumped.
The only thing I can think of is that since I didn't open up the faucets while draining water heater and low point drains, that once I did open them they started running backward into the water heater, creating a siphon that pulled all the antifreeze backward into the water heater and out onto the ground.
The only thing about this theory is that I would think that the water heater outflow had a 1-way valve to prevent backflow (wild guess) or else how would you not normally get antifreeze back into the water heater from the hot water lines past the bypass backing into the water heater on the water heater outflow side? Also, if there was a one way valve, then opening up a hot faucet when draining water heater wouldn't do anything....
I just drained everything again, and am going to just start over and see what happens, but I'm just stumped on figuring out what happened and want to understand it
Probably something obvious, but curious what you pros think?
Thanks!

 

[Rene T]

Chances are you are correct in thinking the check valve has failed. Which is not unusual. It will be on the top pipe which is the hot side. Very easy to replace and cheap if you have access to it. The directional valve could have also failed but not likely.
I would recommend if you do have easy access, remove the check valve and replace it with a regular ball valve and you'll never have issues again. 

Oh, and welcome to the forum.

 

[Gary RV_Wizard]

Opening the faucets or not isn't the problem, but chances are the heater check valve (or the bypass valve) itself is.  If so, antifreeze would have entered the heater tank whether you opened a faucet or not.  It's not a siphon action - just simple water pressure and a leaky valve.

 

[Senator]

If you did not close the low-point drains, all the anti-freeze drained out through that drain.  I had that happen to me.  Be sure they are closed.

If you have both the hot and cold faucet on, the antifreeze can flow through the faucet to the water heater.  Check this option before you replace anything.  It happens even on a residential home.

 

[Ed4000]

Thanks guys for the input and for the welcome! Hope to be a regular here now that we're back on the road again after a long hiatus from RV'ing with kids in college, etc.
Man, this is more complicated than I ever thought it would be with all these valves and bypasses etc. !
I did have the low point drains closed, the antifreeze was only draining out through the water heater. Maybe if I had reinstalled the WH drain plug it would have stopped it from being able to run back?
Ok, I can see the check valve on the water heater outlet side failing (or bypass valve..but less likely) and causing this issue, but here's the big, (probably stupid) question...
Say, on a camper that has no water heater bypass (like the ones I've had before this one), where does the water go that's past the water heater when draining if there is a check valve to keep it from draining back into the water heater tank?
A check valve would also stop the back running antifreeze in the faucet mixing scenario that Senator suggests, would it not?
I wish they had a diagram or something from the manufacturer of exactly what's there, but Keystone has zilch on their website. In fact, the generic owner's manual they supply says to put the antifreeze into the fresh water tank to pump it through the system... "Pour an amount of RV non-toxic anti-freeze into the fresh water tank to fill the tank above minimum
water pump operating level. (Use of a long funnel may be helpful)". This goes against everything I've ever read about the subject.
Maybe I'm just getting too old to understand new stuff, lol.

 

[Rene T]

If you have both the hot and cold faucet on, the antifreeze can flow through the faucet to the water heater.  Check this option before you replace anything.  It happens even on a residential home.

If it's a one bypass valve set up and if the bypass valve is positioned in the bypass mode and both the hot and cold water faucets are opened at the same time, antifreeze still should not get into the heater tank if the check valve is operating correctly.

 

[Senator]

If it's a one bypass valve set up and if the bypass valve is positioned in the bypass mode and both the hot and cold water faucets are opened at the same time, antifreeze still should not get into the heater tank if the check valve is operating correctly.

Isn't the check valve before the water heater, and on the supply/City side of it?  Or are there two check valves, one on each side of the water heater?  I always thought the bypass valve prevented City or tank water from coming into the water heater on the 'IN' or cold side.  I do not think it prevents water from entering on the 'out' or hot side.

In a residence, if you shut off the supply to the water heater, and leave the water main on, then remove the water heater, you will get cold water back through the hot water side in reverse.  This occurs if you have both faucets on.  Not all water will go through the aerator and to the sink.  The cold water runs from the city side, through the faucet, and in reverse through the hot water pipe.

I would think it works the same in an RV.

 

[Rene T]

Isn't the check valve before the water heater, and on the supply/City side of it?  Or are there two check valves, one on each side of the water heater?  I always thought the bypass valve prevented City or tank water from coming into the water heater on the 'IN' or cold side.  I do not think it prevents water from entering on the 'out' or hot side.

You are right although some manufacturers install a check valve on the inlet side of the tank so they say. I've never see one. Typically, you'll have a check valve on the outlet of the heater. The top pipe. If it's a one valve bypass sytem, that valve is actually a directional flow valve. It allows you to either have water go into the tank in the bottom port of the tank OR go up the cross over line where it connects to the hot water line. When in this position, the check valve stops water/antifreeze from going into the heater.
Here is a video showing how to install a one valve bypass system and how it works. It's a little long but it may be very helpful if anyone doesn't understand how it works.

https://www.youtube.com/watch?v=AT67OCaSwGg

On a 2 valve bypass system there is a valve on the cold water line going into the tank and a valve in the cross over pipe going up to the hot water pipe. In normal operation, the bottom valve is open and the valve in the cross over line will be shut. To bypass, just switch those valves. There is still a check valve in the hot water outlet.

in a 3 valve system, there's a valve screwed into both ports of the tank and a valve in the cross over line. Normal operation is the 2 valves screwed directly into the tank would be open and the valve in the cross over line would be shut. To bypass, just switch these valves. The 2 valves screwed into the tank will be shut and the valve in the cross over line would be open allowing antifreeze to flow through from the cold side to the hot side.
There is no check valve in this set up.

 

[John From Detroit]

Re Check valves. IF You have a 1  valve bypass system the check valve is on the OUTPUT side of the heater.. Some companies put on on the inlet as well but why??????

IF you have a 2 or 3 valve system it's not needed but again some put 'em on.

 

[mel s]

You are right although some manufacturers install a check valve on the inlet side of the tank so they say. I've never see one.

Rene T
The check valve on the Suberban water heater in my '96 Safari coach, as built by SMC, is in the cold water supply line.

 

[Rene T]

Rene T
The check valve on the Suberban water heater in my '96 Safari coach, as built by SMC, is in the cold water supply line.

You should also have one on the top pipe for the hot water coming out of the heater unless you have a munually operated valve there.

 

[Senator]

You should also have one on the top pipe for the hot water coming out of the heater unless you have a munually operated valve there.

A question for my learning.  If the bypass valve is ON, and you have either the pump on, or city water, can you get water out of a hot faucet?  Or does the bypass valve totally block the hot water side altogether?

My fifth wheel is in storage, or I would test it myself...

 

[Rene T]

Yes you will get cold water out of all the hot water faucets. Remember though, that if your water heater tank is empty, DO NOT turn on the propane or accidentally turn on the electric element if you have that option.