[Homestead31]

hi all - i have to swap out the expansion tank on my hot water heater. i'm a first timer on this project, but after watching some videos it seems pretty simple. the question i have however is about matching the pressure in the tank to the water pressure. I have not been able to locate a pressure gauge on the water line, so i really don't know what the pressure is. it is possible that the pressure gauge is up in the basement ceiling, which has been sheet rocked over.

i am assuming that i won't be able to use the old expansion tank as a guide b/c the bladder is likely busted, which is why i am replacing to begin with.

any thoughts here? should i go toward the top of the pressure range? the bottom? right in the middle?

thanks

 

[joecaption]

Go to Lowes or HD and pick up one of these.
https://www.supplyhouse.com/Bluefin-GW25-300-Water-Test-Gauge-3-4-Hose-Thread-0-300-PSI
If your on city water there may not be a gauge.

 

[Plumbear]

any thoughts here? should i go toward the top of the pressure range? the bottom? right in the middle?

thanks
[/QUOTE]

Nope. You should inflate your tank to house pressure, minus 2 psi. This instruction is included with most tanks. There are several reasons, but the big ones are
1) This allows some water to fill into the tank, compressing the bladder, so that it can react to and absorb pressure spikes, with say, the miniscule expansion caused by the water heater.
2) It also allows for some air loss over time with a bit of reserve functionality.

To measure the house pressure, install the new tank, measure the pressure at the schrader valve on the new tank. NOT THE OLD TANK. The old one will have water at the valve, likely destroying your tire gauge.

Now remove your new tank, bleed the pressure down to house -2 and reinstall it. (Or fill to that pressure). If your house is over 75 psi., you need a pressure reducer, or need to adjust your pressure reducer. As they age, they get to where they don't function.

Plumbers overfill a tank at the shop, and then use a timed bleed down, but this is the simple method.

Oh, and buy a cheap digital tire gauge. They're pretty cheap, pretty accurate. Don't get water in it.

 

[chandler48]

@Plumbear I believe the OP is installing an expansion tank and not a well pressurization tank. Oh, it's a 2 year old thread, so hopefully it is already installed.