Yet another Vacuum Relief Valve question

[JAGDIY]

Hi Experts!
I had a great conversation with the Chief Plumbing inspector for my city in NC today regarding the new hybrid hot water heater I'm about to install (replacing a gas unit) and he made me aware of

504.2 Vacuum Relief Valve

Bottom fed water heaters and bottom fed tanks connected to water heaters shall have a vacuum relief valve installed. The vacuum relief valve shall comply with ANSI Z21.22.

I'm very clear about the valve being installed higher than the top of the tank-portion of the hot water heater, however, in all the installation instructions I've seen, such as, https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/11945-source, it seems to show the valve being the highest point in the plumbing line, not just higher than the hwh. In my case the hhwh is in a mechanical room in the finished basement. It is not possible for the valve to be the highest point. In addition, the cold supply to the hot water is running just below the joists so in my scenario the 90 on the line-in side to the T for the valve pictured below would be rotated 180 degrees (so up, not down.) Is this okay and will the valve still be able to do it's thing if a vacuum scenario were to occur?

Thank you in advance.

 

[Reach4]

I think you are worrying about something that you should not worry about.

Your https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/11945-source link says this:

Install No. LFN36 in cold water supply line with or above the highest point in the tank. No. LFN36-M1 must be installed vertically in an upright position as shown.​

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[Terry]

A vacuum relief for electric water heaters is to prevent a siphon from the water heater. It does need to be on the cold supply for the water heater. You don't need it for anything else.

 

[JAGDIY]

Thank you @Reach4 and @Terry. I believe I got the wrong impression about the valve position after reading so many threads on it. Thank you for clearing that up.

I have semi-related follow up question. Please let me know if it should be a new thread. I am also trying to determine if I should have a single service expansion tank installed for the water heater. I am on a well and as such I have a pressurized well tank. In the first hot water heater install some years back, the plumber indicated this would serve the role of the water expansion tank needed by the hot water heater. My concern is there are now three Kinetico well water treatment tanks between the hot water heater and the pressure tank: Two remove iron (using "Macrolite", it is not a softener) and one is a holding tank that mixes soda ash slurry into the water to raise the ph. If this were your setup would you install an expansion tank, a thermal expansion relief valve or nothing more downline from those tanks? Thank you again.

 

[Reach4]

If this were your setup would you install an expansion tank, a thermal expansion relief valve or nothing more downline from those tanks?

No, probably. Reasons to install thermal expansion tank: as water heater expands water and there is no check valve:

1. water expanding toward the pressure tank will register as a small "phantom" flow.
2. if there is only a short length of pipe between the WH and the softener, the expanding water is hot and could heat up the softener too much.

To stop those, a check valve after the softener and a pressure tank at the WH would be needed. I don't use a check valve or thermal expansion tank. I figure the the phantom flow will not be a lot and will not speed up my regenerations significantly. Also, I have maybe 10 ft of pipe, so really hot water should not be able to expand as far as the softener.

 

[JAGDIY]

Thank you @Reach4 ! Sounds like we have a similar setup. I have at least 12 feet of 1" uponor propex between the treatment tanks and the hot water heater. I've not had a problem with the current gas hot water heater with this setup, but figured now is the time to address things, if needed. Cheers!!

 

[Reach4]

Musings:

I thought about the rationale for 804.2. I guess it is to prevent siphoning out the water when the water pressure drops. If I had a not-bottom-floor top-feeding WH, I would put in a vacuum relief. Some places require them on all new WHs. I presume that is to KISS -- avoid having to analyze where it is actually needed. Like why did IPC forbid PVC for all indoor pressurized water because CPVC is better for hot? I am thinking there may be a defacto acceptance of indoor pvc before the well pressure tank.

I don't know that I have ever seen a bottom feeding WH, tho I know that the drain port on WHs with two top ports is often used as a return path in gravity-powered HW recirculation systems.

For more to worry about, see https://terrylove.com/forums/index....for-softener-filter-on-input-or-output.63102/ I have no vacuum relief valves; I know I am taking a finite risk.

 

[JAGDIY]

I enjoy reading the musings @Reach4 . I also read the aforementioned thread, along with about every other mentioning vacuum breaker or vacuum relief valve, before my post yesterday. Seeing that tank that looked a lot like my mixer is what caused me to decide I must ask the experts about all this.

FWIW, I do believe bottom feeding water heaters will become much more common as more people move away from traditional electric WH (and even gas) to the Heat Pump WH. Having to move/extend both hot and cold lines is the biggest hassle with this 65 gallon beast. Condensate disposal in the basement mechanical room is a minor hassle. Having the mechanical room, which sets within the finished basement inside the building envelop is the biggest reason I'm switching to this unit. Saving about $100/year over gas is a plus.

 

[Jadnashua]

IF there's a check valve between your pump's storage tank and the WH, yes, you need an expansion tank. But, if water can easily flow without restriction back into your bladder tank, it isn't necessary unless there's a code issue that I'm not aware of.

IOW, there must be someplace for the expanding water resulting from heating the water to go and a well tank is essentially an oversized expansion tank so would suffice. A closed system without expansion can easily get high enough to open the T&P valve on your WH which should open at 150psi...more than your water softener is likely to like!