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Potable Expansion tank

Good morning. My potable expansion tank for my hotwater heater is pierced on the tank and has a slow leak. Do I need to replace it or can I just cap the opening that it is attached to? Do I need the expansion tank? Thanks for the time.

Re: Potable Expansion tank

Yes, I would say that you need the replacement tank----not only for the fact that 1)the old one has been on there for some time; and 2) water expands 5% when it's heated; if your HWH is the typical 40 gal size, that means that the heated water will expand to 42 gal.---this water has to go somewhere---if there is a pressure relief valve (as there should be) it will always be opening & spilling water on the floor every time the heater heats up the water.

I would replace it with the model listed on the nameplate of the old one, or you could get an Amtrol ST-5 designed for potable hot water systems for approx. $40 at heating supply houses in your area---if your HWH holds considerably more than 40 gal., post back with the actual capacity listed on the HWH; if there is no nameplate on the old ET, we can look up a suitable replacement according to HWH size.

These ETs are rated for approx. 40 psi; don't buy the one at HD/Lowe's that is rated at 12psi & is designed for heating systems.

Re: Potable Expansion tank

Thanks for the reply. The HWH is a Bradford White 40gal 151.4 liters. The Expansion tank is a WATTS REGULATOR which looks to be the one on Home Depot's site. If I replace it then I just need to shut off the main water, drain the lines, unscrew the tank, and replace, correct? Or is it a job for a plumber? Thanks again for your time.

Re: Potable Expansion tank

Be very careful what you buy at Home Depot/Lowe's---most of the clerks are not familiar with the subtle difference is heating/plumbing products---this specifically applies to heating equipment & expansion tanks.

On top of that, Watts Regulator has scores of different model expansion tanks available---most are designed to be used on non-potable heating systems--this is not the tank you want.

Try & see if there is a specific model number on the old ET---something like DET-12-M1, or DET-5, or PLT-5; all of these Watts ETs are for POTABLE hot water heaters in the 40 gallon range.

If you want to diy, you might be better off consulting the Yellow Pages under "Heating Equipment--parts" and going to a wholesale parts house in your area, most will sell to homeowners these days.

Specify that you want the ET for a 40 gallon hot water heater; as a first step, buy a water pressure gauge at HD/Lowe's that attaches (screws on) to your outside garden faucet, turn it on & read the psi pressure of your water system (probably anywhere from 20 psi to 60 psi); the counterman at the parts house can then sell you the right model ET.

To attach the new ET, turn off the water supply & lift the little lever on the pressure relief valve to make sure there is no water pressure left in the line near the old ET; turn the old ET by the body with your hands to remove (or a wrench if it won't budge), & wrap some telfon tape clockwise on the male fitting of the new ET & screw it firmly in place on the female fitting; use an air pressure gauge on the little "bicycle tire" fitting (Schrader valve) at the bottom of the ET to determine the air pressure of the new ET & inflate it with a bicycle tire pump to the water pressure reading you got with the water pressure gauge.

Most potable ETs come with an air pre-charge of 40 psi, but the low-cost Watts PLT-5 ($31.00) is pre-charged at 20 psi & you can pump it up at the Schrader valve to whatever you got on the water pressure gauge.

It turns out that the hot water in a 40 gal. HWH will probably expand only 1/2 gal. at any given time, since only a portion of the 40 gal is kept hot at any one time---this is still enough to open the PRV & spill water onto the cellar floor, so the ET is definitely needed.

Check the sites below to get a ballpark figure for what the various ETs will cost---enter the product brand or model number in their search box.


Re: Potable Expansion tank

Thank you so much for your time and advice on this. I really appreciate it.

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