No hot water flow, stopped up ?

MrWizard wrote:
What is the reason for the check valve in the output ?

Stop cold water being syphon into the tank when the water in the pipes cools after the faucet/shower has been turned off ?

I don't have a replacement, and unless its a safety reason, I'm not going to replace it, as long as it operates without it

I want max flow hot water !!

The check valve is part of the winterizing by pass kit. The bottom of the heater has 3 way valve, and the top has a check valve so the antifreeze will not go backwards into the heater and use up 6 gallons of antifreeze. Or 10 gallons if you have the bigger heater.

Here is the kit installed from Sunline.

You can see the brass check on top


The yellow arrow is pointing to the 3 way valve on the bottom.


This is another model then the one above. Same setup


During the heater unhooking process, you can see the white plunger in the check valve on the top fitting.


I myself do not like the check valve setup after having so many failures with them as the camper gets older. I restore older water damaged campers. Every heater I pull out gets a 2 valve bypass added to get rid of the plastic straight thread PEX fittings the factory used which leak as time goes on and eliminate the check valve.


This may not work in your case as you have no room for it at the back of the heater, just showing you so you know what it does.

I use brass machined hex nipples to correct the plastic straight running thread fitting issue, then remove the check and top Tee, and install a Flair-It 3 way valve. This becomes a 2 valve bypass setup.


You talked about removing the check, the system will work normally without the top check valve, the issue comes when you want to bypass the heater to add RV antifreeze.

Good luck on your cut and hassle project. I know they can be frustrating.

John