Improved hot water heater bypass

[steamboatscott]

I'm thinking of changing my one-valve hot water heater bypass to a two-valve system. The single valve works fine for bypassing the inlet to prevent antifreeze from entering. But recently, I noticed a foul taste coming from the water heater and bypassing it didn't prevent that water from entering the pex tubes. I had to drain the heater to prevent any of its water from coming through the outlet and then I noticed some air coming out and into the hot water line.

Am I crazy/missing something?

[chuckster57]

If the valve is operating correctly AND the one way valve at the hot out is good, you shouldn’t get any antifreeze into the tank. 2 valve bypass was common for years, I suspect 1 valve was to save weight LOL.

[flybouy]

Originally Posted by steamboatscott

I'm thinking of changing my one-valve hot water heater bypass to a two-valve system. The single valve works fine for bypassing the inlet to prevent antifreeze from entering. But recently, I noticed a foul taste coming from the water heater and bypassing it didn't prevent that water from entering the pex tubes. I had to drain the heater to prevent any of its water from coming through the outlet and then I noticed some air coming out and into the hot water line.

Am I crazy/missing something?

Sounds like you need to flush the fresh water tank and the entire system. The only way to get water out of the hw tank and into the water lines is if the valve is bad or not turned off compleyly. The only way for air to enter is if you manually open the blow off valve or pull the drain plug.

[bobbecky]

The one valve bypass, along with the check valve on the hot water outlet is needed for water heaters that do not have access the the back of the units where valves would be installed. As long as that check valve is functioning, you are good. Like what was said, flush your fresh water system and sanitize it and your problem should go away.

[WNY Bullet]

I couldn't get my one valve/backflow setup to ever work correctly, so I replumbed it to a three valve setup. The three valves I added was Cold IN, Hot Out, and By-Pass. I also removed the back flow since it isn't needed anymore.

[JRTJH]

Originally Posted by WNY Bullet

I couldn't get my one valve/backflow setup to ever work correctly, so I replumbed it to a three valve setup. The three valves I added was Cold IN, Hot Out, and By-Pass. I also removed the back flow since it isn't needed anymore.

That's exactly how the water heater "bypass system" was plumbed 30 years ago. The "industry simplification" (really cheaper method) was to install a one way valve on the hot water outlet and a single diverter valve on the cold water inlet.... It "works the same (except for cold flashes while showering) and saves the factory several bucks per unit.... Your system is my "go to when there's a problem" and I've installed the 3 valve bypass on all of my trailers "when the existing one way valve fails"....

[flybouy]

The only issue with the 3 valve system is the possibility of confusion among the end user with which valve goes in which position. After winterizing folks would forget how the valves were oriented then have issue in the spring. Not an issue for folks with some experience or mechanical understanding but I have a BIL that I had to make a drawing for years ago (pre cell phone cameras). It's a lot easier to tell someone to "turn the one valve the other way".

[JRTJH]

Originally Posted by flybouy

The only issue with the 3 valve system is the possibility of confusion among the end user with which valve goes in which position. After winterizing folks would forget how the valves were oriented then have issue in the spring. Not an issue for folks with some experience or mechanical understanding but I have a BIL that I had to make a drawing for years ago (pre cell phone cameras). It's a lot easier to tell someone to "turn the one valve the other way".

Yep, we have "enough confusion with only one valve"... Imagine if every owner had to learn to play a trumpet (3 valves) to winterize or dewinterize their trailer ....

[Mic]

thanks a lot of PEX clamps!!!!

[steamboatscott]

I'm probably going to install the 3-valve setup in my RV as well. It worked flawlessly in my last trailer and ensured that I NEVER had water coming from my hot water tank if I didn't want to whereas I have confirmed that the single valve system can easily let pressurized water from the hot water tank into the cold lines even if the single-valve bypass is enabled. For example, if the water pump is off and I call for cold water, pressure from the water heater pushes it's supply into the cold lines.

I'm an engineer, so I like to overengineer and have complete control

[flybouy]

Originally Posted by steamboatscott

I'm probably going to install the 3-valve setup in my RV as well. It worked flawlessly in my last trailer and ensured that I NEVER had water coming from my hot water tank if I didn't want to whereas I have confirmed that the single valve system can easily let pressurized water from the hot water tank into the cold lines even if the single-valve bypass is enabled. For example, if the water pump is off and I call for cold water, pressure from the water heater pushes it's supply into the cold lines.

I'm an engineer, so I like to overengineer and have complete control

If the hot water is "pushing past" the valve it sounds like it could be excessive pressure from expansion. When you purge the air from the system are opening the water heater valve on top of the heater that drains out to the open air?

[steamboatscott]

It's definitely excess pressure. Doesn't happen if I go flip the pressure relief valve a bit. Like I said, I like to overengineer and know that a switch has totally disabled something. For example, if hot water is tasting / smelling weird, I flip one switch. The one-valve setup doesn't provide that but instead requires me to go outside and relieve pressure and probably just drain the tank.

[WNY Bullet]

Originally Posted by Mic

thanks a lot of PEX clamps!!!!

Clamps are cheap, peace of mind...Priceless!

[flybouy]

Originally Posted by steamboatscott

It's definitely excess pressure. Doesn't happen if I go flip the pressure relief valve a bit. Like I said, I like to overengineer and know that a switch has totally disabled something. For example, if hot water is tasting / smelling weird, I flip one switch. The one-valve setup doesn't provide that but instead requires me to go outside and relieve pressure and probably just drain the tank.

Overengineering is fine but all I'm saying is if you are reliving all the air from the water heater and you add the "3 valve system" you could end up with a leak. The top of the water heater needs to have an air pocket to allow the water to expand when heated. If you remove that air pocket then when the water gets hot and expand it could cause a problem.

[JRTJH]

Originally Posted by steamboatscott

It's definitely excess pressure. Doesn't happen if I go flip the pressure relief valve a bit. Like I said, I like to overengineer and know that a switch has totally disabled something. For example, if hot water is tasting / smelling weird, I flip one switch. The one-valve setup doesn't provide that but instead requires me to go outside and relieve pressure and probably just drain the tank.

The "correct procedure" to fill the water heater is to ESTABLISH an air gap in the tank. To "flip the pressure relief valve a bit" ELIMINATES the air gap in the tank...

Take a look at the correct tank fill procedure recommended by the manufacturer on page 6 to "reestablish the air gap" which prevents, in most cases, the relief valve weeping. Atwood water heaters have a similar procedure to reestablish the air gap in that brand.