Location For Expansion Tank - Before or After WH Shut-Off

[teamarrows]

Greetings from a new member.

Is there a specific reason why an expansion tank is installed between the water heater and the water heater shut-off? Wouldn't it still do its job if installed anywhere in the system?

Thanks.

 

[Twowaxhack]

It should be installed on the cold line and will do its job installed any place aslong as it’s not separated from the source of expansion by a check valve/ backflow preventer or any closed stop valve.

 

[teamarrows]

Thanks for the prompt response.

That's what I thought. So many videos show the installer putting them after the shut-off, with a couple even saying that is where they are supposed to be installed.

I can't think of a reason why it matters, so I'm glad I asked. It'll give me more options when I install mine.

 

[Twowaxhack]

Thanks for the prompt response.

That's what I thought. So many videos show the installer putting them after the shut-off, with a couple even saying that is where they are supposed to be installed.

I can't think of a reason why it matters, so I'm glad I asked. It'll give me more options when I install mine.

Some codes require it between the water heater and the cold water stop valve.

This prevents a closed system if the owner turns the water off to the heater and doesn’t turn the water heater power or fuel source off and doesn’t relieve the pressure

 

[skeezix]

If you install something on the inlet side of the shutoff valve you hafta find another shutoff valve before you can replace whatever you installed. Usually that means a trip to the meter.

 

[Twowaxhack]

If you install something on the inlet side of the shutoff valve you hafta find another shutoff valve before you can replace whatever you installed. Usually that means a trip to the meter.

Yet showers and tubs don’t require service stops.

 

[teamarrows]

Some codes require it between the water heater and the cold water stop valve.

This prevents a closed system if the owner turns the water off to the heater and doesn’t turn the water heater power or fuel source off and doesn’t relieve the pressure

Would that closed system be any different than the closed system that exists when there is no expansion tank in an already closed system?

IOW any more dangerous/detrimental than what already exists?

 

[Twowaxhack]

A closed system is a closed system no matter how it happens.

If you have a closed system now it should be addressed.

 

[teamarrows]

A closed system is a closed system no matter how it happens.

If you have a closed system now it should be addressed.

Exactly. The question is the best way to address it.

I have an easy, out of the way place to plumb in the tank. One T in a wide open space, easy means to support the tank, no check valve/backflow preventer between it and the WH, etc. However, if it really should be between the WH and the shut-off, it'll take some work and be in a location that is less convenient. It's certainly doable, but not where I'd prefer to put it - unless I move the shut-off too. Just more work.

Thanks for all the input.

 

[Twowaxhack]

You can place the tank anywhere you want in the cold system as long as the tank and the water heating equipment is not operated if the two are separated by a turned off stop valve or a check valve.

Stop valve for the water heater should be within three feet of the heater.

 

[teamarrows]

You can place the tank anywhere you want in the cold system as long as the tank and the water heating equipment is not operated if the two are separated by a turned off stop valve or a check valve.

Stop valve for the water heater should be within three feet of the heater.

I figured there would a specified distance for the shut-off. I'll tag the WH shut-off with a warning/instructions as a precaution.

I'll make it a durable, hard to remove, tag. ⛓

 

[Twowaxhack]

I figured there would a specified distance for the shut-off. I'll tag the WH shut-off with a warning/instructions as a precaution.

I'll make it a durable, hard to remove, tag. ⛓

You’re the boss ✌ I personally wouldn’t even tag it.

Maybe just write the location of the expansion tank on the water heater. . I probably wouldn’t even do that

 

[teamarrows]

BTW...how much "expansion" will a tank absorb? 40 gal tank, 55-60 PSI from PVR, 55°F in, 120° - 125°F out, so I'm assuming a 3.2 gallon tank.

Somebody told me it might drop the recovery PSI by 5 - 10 PSI max. I'm getting more than that right now, but I'm sneaking down to the 120° - 125°F range on the new tank. i.e. the tank is running hot right now, about 135° last time I checked.

 

[Twowaxhack]

3.2 tank will work. Set it about 5psi higher than your water pressure.

 

[teamarrows]

3.2 tank will work. Set it about 5psi higher than your water pressure.

Is that to allow for the excess rise in PSI during recovery?

 

[Twowaxhack]

Is that to allow for the excess rise in PSI during recovery?

No, just makes sure your tank pressure stays above your water pressure. You could go up to 80 psi. Expansion control would kick in at 80psi if you did.

The tanks general purpose is to allow for expansion and the resulting pressure increase during recovery.

 

[teamarrows]

No, just makes sure your tank pressure stays above your water pressure. You could go up to 80 psi. Expansion control would kick in at 80psi if you did.

Well, I'm already over 80 after recovery. Hope that goes way down once I get the temp to settle in at 120°-ish.

The tanks general purpose is to allow for expansion and the resulting pressure increase during recovery.

That I know...that's what I'm trying to resolve. But I still don't understand why the tank should be set 5 psi higher. What purpose does that serve? (I've never seen that mentioned in any videos/instructions)

Theoretically, based on that suggestion, if the recovery spike drops to only 5 over my PVR set point once I get the temp down to 120°, then I wouldn't even need a tank.

 

[Twowaxhack]

The expansion tank allows the expanding water to compress the air charge that you put into the expansion tank rather than spike the system pressure.

I like to exceed my water pressure by a few pounds to insure My air charge is more than my water pressure. This insures my tank is sufficient for my application. It allows for the gauges to be off a little and not affect the tanks performance.

Follow the directions that come with the tank.

Its easy, goodluck to you.

 

[hdtvkeith]

I oversized my expansion tank because during winter my tap is around 55F and my water heater is set to 140 and with variation can generate water anywhere from 135-145 depending on how much was used and replaced and how long it sat. On my to gallon gas heater I use a 4.5 gallon expansion tank. I was told that is larger than needed, but a few extra $$ for piece of mind for me is fine. Twice a year I drain the tank, release pressure from water lines and double check pressure in expansion tank to the house pressure. My expansion tank it at least 15+ pipe feet away from heater. There is a shutoff at the heater and one as soon as the main enters the home. I never close the heater shutoff without putting the heater into Vacation/pilot mode.

 

[Twowaxhack]

I oversized my expansion tank because during winter my tap is around 55F and my water heater is set to 140 and with variation can generate water anywhere from 135-145 depending on how much was used and replaced and how long it sat. On my to gallon gas heater I use a 4.5 gallon expansion tank. I was told that is larger than needed, but a few extra $$ for piece of mind for me is fine. Twice a year I drain the tank, release pressure from water lines and double check pressure in expansion tank to the house pressure. My expansion tank it at least 15+ pipe feet away from heater. There is a shutoff at the heater and one as soon as the main enters the home. I never close the heater shutoff without putting the heater into Vacation/pilot mode.

What size water heater do you have ?