Bottom Fed Water Heater Heat Trap?

[Brono]

Good afternoon,

I just installed a Superstor SSU-45N, and it is bottom fed unlike my old one which was top fed. I’m getting a lot of convection coming back up the cold water line, and I’m wondering if you need a heat trap on a bottom fed, or is there some expected loss as a result of its design? Didn’t know if I could also use a check valve to prevent the backflow but not sure how that would interrupt the vacuum breaker. I would imagine that would nullify it. Photo of the installation attached, any input is appreciated! Don’t mind the shark bite 90, the supply house was out of the PEX to copper ones. Ordered one online and will replace once it gets here. Still have to run the overflow drain hose as well.

Thanks and open to any feedback on the install as well!

Edit - Spelling

 

[Fitter30]

Heat trap is a inverted trap or nipples.

https://www.supplyhouse.com/Sioux-Chief-636-3TR-3-4-Heat-Trap-Loop?utm_source=google_ad&utm_medium=Shopping_ntm&utm_campaign=Shopping_NTM_New_users&gclid=EAIaIQobChMI4LHtrNnq-gIVHCytBh3w0wICEAQYASABEgJoT_D_BwE

Everbilt Dielectric Nipple Heat Trap 15009 - The Home Depot

These metal and plastic dielectric heat traps help save energy by preventing heat loss through the inlet and outlet pipes of a water heater while the heater is idle. Measurements are 3/4 in. NPT x 3/4

www.homedepot.com

 

[Sponsor]

 

[Brono]

Heat trap is a inverted trap or nipples.

https://www.supplyhouse.com/Sioux-Chief-636-3TR-3-4-Heat-Trap-Loop?utm_source=google_ad&utm_medium=Shopping_ntm&utm_campaign=Shopping_NTM_New_users&gclid=EAIaIQobChMI4LHtrNnq-gIVHCytBh3w0wICEAQYASABEgJoT_D_BwE

Everbilt Dielectric Nipple Heat Trap 15009 - The Home Depot

These metal and plastic dielectric heat traps help save energy by preventing heat loss through the inlet and outlet pipes of a water heater while the heater is idle. Measurements are 3/4 in. NPT x 3/4

www.homedepot.com

Thanks I wasn’t sure if those would work in a horizontal due to the ball needing to float? Also does is completely seal off in the event of backflow? Not sure if they work with the vacuum beaker

 

[WorthFlorida]

A simple check valve should work on the inlet side. Is the expansion tank on the hot side or is it for a hydronic heating system? Where is the vacuum breaker? The T&P discharge pipe needs to terminate between 6" to 1.5" (2x3/4") from the drip pan.

 

[Brono]

A simple check valve should work on the inlet side. Is the expansion tank on the hot side or is it for a hydronic heating system?

Unfortunately it is on the hot side, as it was when we bought the house. I was going to move it but ran out of time and just needed the hot water back.

The check valve seems like the easiest solution but would that interfere with the vacuum breaker? I don’t fully understand the scenario that it would be used. If something is pulling vacuum from the hot side i believe it would work, but if it’s vacuum from the cold coming from the city (seems like the most likely scenario) wouldn’t the check valve slam shut?

Edit - spelling

 

[WorthFlorida]

Where is the vacuum breaker? Not sure why why it would be affected? Heat trap nipples will only work in the vertical position. As you stated, gravity plays a role.

It's the expansion tank that is causing the problem. As cold water is drawn the pressure drops. The expansion tank also pushes back on the hot water side, thus forcing through the tank to out the cold side trying to equalize the pressure between the hot and cold.

If the expansion tank is set to 60 PSI because that was the static pressure of the cold water side and without water flowing the hot side will be the same. When cold water is drawn, the pressure might drop to 55 PSI, thus the 60 PSI of the expansion tank will push the water through the tank until it is 55 PSI.

Since you are in RI (Northeast) where most homes have hydronic heating systems that require expansion tanks, most think all expansion tanks should be on the hot side. For water heaters it needs to be on the cold side.

 

[Fitter30]

Vacuum breaker would let air in if tank was draining with no water pressure. Doesn't work as a heat trap nipple.

 

[WorthFlorida]

I found the vacuum breaker in the picture.

This is the installation manual. An excellent publication with many different installation needs. Most of them show a mixing valve and the expansion tank on the cold inlet side.

https://htproducts.com/literature/lp-83.pdf

 

[Brono]

I found the vacuum breaker in the picture.

He is the installation manual. An excellent publication with many different installation needs. Most of them show a mixing valve and the expansion tank on the cold inlet side.

https://htproducts.com/literature/lp-83.pdf

Thinking it through the vacuum breaker would work either way - that was a dumb assumption on my part. I was thinking that since it wouldn’t have a direct line to the water heater if the check valve slammed shut it wouldn’t work- that’s not the case the moment vacuum starts being pulled the breaker will do it’s job. Wouldn’t matter if there isn’t a direct air path between it and the tank, just needs to prevent vacuum ever being created.

I believe the vacuum breaker is in a satisfactory spot, being above the highest point of the water heater, and upstream of it. I opted to not do a mixing valve as we haven’t had an issue with capacity (yet).

As for the check valve, will it have any negative impact on the expansion tank in it’s current configuration? Only thing I could think of is a slight build of static pressure on the hot side? The pressure coming into the house is just shy of 80psi, when I replaced the expansion tank last year I set it to match that, roughly ~75psi.

Edit - if I’m draining down my domestic lines & tank to install the check valve, I may as well move the expansion tank at the time. The check valve would need to be upstream of the tank I believe, which is still a decent distance to have heat escape up the lines. I won’t have warm water coming through a cold side point of use, but still a loss of efficiency. Seeing as the nipples require gravity is there any other way prevent the water creeping up? Or is it not as big a loss as I’m making it?

 

[WorthFlorida]

Do not use check valve with the expansion tank on the cold side. It will prevent the expanding pressure from heated water to be compensated by the expansion tank. If you want a heat traps, install a loop type on both sides.

 

[Reach4]

A check valve upstream of the thermal expansion tank should be OK. But it is not going to stop convection flows downstream of the check valve.

What brand is that red PEX?

 

[Brono]

A check valve upstream of the thermal expansion tank should be OK. But it is not going to stop convection flows downstream of the check valve.

What brand is that red PEX?

It’s Legend Hyperpure. Had some leftover from a previous project, but not enough blue unfortunately. Small detail but oh well.

 

[Reach4]

It’s Legend Hyperpure. Had some leftover from a previous project, but not enough blue unfortunately. Small detail but oh well.

Are you using expansion fittings with that?

http://www.legendvalve.com/images/HyperPure/hp-brochure-webv2.pdf says

HyperPure™ is compatible for use in plumbing systems
utilizing ASTM F 1807 and 2159 PEX fittings with either
copper rings or stainless steel clamps. It is also compatible
with ASTM F 2080 cold expansion PEX fittings and ASSE
1061 push-fit fittings.

It looks like you are using F1960 fittings. Maybe I am mistaken, or maybe the document I linked to has been superseded.

https://pexhouse.com/what-are-the-types-of-pex-fittings/ writes about the different types.