Whats this valve for?

[K/C and Pups]

Hi Folks. I am in the process of eliminating my 3/8" polybutylene tubing with 1/2" pex, and discovered this loop with a shutoff valve between the cold supply and the hot return. After some head scratching, I still cannot determine the necessity. The valve, as pictured is closed. I assume if I needed to work on, or disconnect the water heater, the valve could be opened creating a flow return of cold water to the fixtures thru the hot line, but the same effect would be achieved with both supply and return valves off, although the return line would no longer be pressurized, therefore no flow.
My question is - does everyone have this loop, and if so, is it necessary.
Thanks
Charlie

[cook elandan]

I my unit the water system is in series.  If you lost you hot water tank you can turn the valves to remove the tank but still have water to you system. IMO.

[lemortede]

That is the water heater bypass.
Its typically used for winterizing.
You close the valves that let water in and out of the water heater and open the bypass valve.
The water heater typically has its own drain on it and you are able to ensure that all the water is out.
With the water heater out of the system you can get the RV antifreeze into the hot lines.
This makes it so that you only have to use enough RV antifreeze to fill the lines rather than the lines plus the water heater (6+ gallons).
You can also use it to bypass if there is an issue with the water heater.

[K/C and Pups]

Thanks. I understand the bypass, however, other than the winterizing, which I hope I never have to be concerned with in Phoenix, I assume by closing the 2 valves, and disconnecting the water heater at the source. my cold water would dead end at the valve and all fixtures would still be pressurized with cold water while the heater was out. In the picture there are approximately 21 fitting connections. If I could get copper in this motorhome, with soldered connections, that would be my route, but that would also mean tearing out every cabinet and some floors to accomplish. Hence the pex tubing. Goal is to eliminate fittings, and potential future leaks.
Thank You

[Rickf1985]

Copper with soldered connection would be leaking in a month! It will work harden from the vibration of movement. That is why the plumbing on these is plastic.
Funny, I look at all of those wiring butt connectors just like you look at all the plumbing fittings. Problems waiting to happen. W%

[K/C and Pups]

Thanks Rick. Your right about the copper. Ridged pipe needs to remain ridged. I am also worried about the number of Pex connections. The existing plumbing snakes around in locations with no access. I considered a manifold with home runs, but that would require a 3/4" manifold for 1/2' pipe. My fresh water tank feeds a 1/2" line and the existing pump is 1/2". I may build a removable insulated steel chase under the floor, between the frame rails, to pipe across the hallway. If not, I have to feed the pex through the double floor. or rip out the existing floor.  Either way the pipe would be hard to access later. When done I will have 8 tee fittings, and hopefully I can get to them if they leak.

[Rickf1985]

I agree that what was done at the water heater could have been done with less fittings just by mounting the valves directly on the heater. That alone would have eliminated a lot of fittings. The newer fittings, if done right, are pretty dependable. It is the older polybutyl tubing that had all kinds of issues.

[fasteddie313]

I put 120psi of air on my kitchen faucet and blew everything out switching hot and cold, cycling drain plugs and other faucets until I couldn't even get any more mist..


Hope that did the trick..


Great way to find and fix all your leaks too.. If she holds 120psi of air she'll hold 20 psi of water. Think I got em all now..