Expansion tank due replacement

[wmn]

I have an expansion tank needing replacement, pressure relief valve on WH spits out water when heater reheats after a shower. Expansion tank is screwed directly to a copper fitting (No dielectric) and has signs of a small leek. What's the best way to install a new tank? 6" brass nipple and Female coupling, Brass union or dielectric union? Can I put a brass ball valve in between the copper fitting and the tank to facilitate the next tank replacement? Been in the house 10 years and found that's about the average lifespan of the expansion tanks.

 

[Reach4]

Best is that the tank hangs down. A valve just above the tank, that can be closed to make changing the tank easier, is fine. Normally not a union. Tank hanging down can let you detect water leaking past the bladder.

Consider posting the current situation as a photo.

Thermal expansion tanks should normally be empty of water. The air precharge should be the the same as the normal water pressure from your city water pipeline, or a tad higher. The tank should normally be empty of water.

 

[Sponsor]

 

[wmn]

Yes, the tank does hang down. Was thinking a F x M ball valve.

 

[Reach4]

Is there water in the tank now? I presume yes, and water would come out of the Schrader valve. Also, when you knock on the tank, it should sound hollow. If there is not water in the tank when things are in static stte, it may just be that the existing tank is undersized.

I would not add a nipple in addition to your new valve. I don't know what the thought is on dead legs as it applies to thermal expansion tanks. It seems better to me to not add the nipple plus the new valve. I am not a plumber. I know that my earlier ideas of using a longer pipe to remote the tank is not liked.

 

[wmn]

The leak appears the be on top at the connection between the male tank fitting and the female copper fitting. Not sure if there's water in the tank, but no leak at the air charge port.

 

[Reach4]

The leak appears the be on top at the connection between the male tank fitting and the female copper fitting. Not sure if there's water in the tank, but no leak at the air charge port.

If there is not water in the thermal expansion tank, you need a bigger tank. But your mounting situation would not handle a bigger-diameter tank. I would check for water, and if there is no water, then things will get more complex. I would then consider doing some soldering to move the tee a little to accommodate a bigger tank.

A tiny water leak would make it less likely to get discharge at the T&P valve after a hot shower.

If the problem was just a leak at the threads, tightening the tank another 1/4 turn might cure the tiny leak.

 

[wmn]

Thought about trying to tighten a little but it's been there for 10+ years. Afraid it's corroded in place and a little tighting might cause a bigger problem. Also concerned about the dissimilar metal corrosion, hoping the brass valve might improve the situation.
It has been fine up until about 2 months ago.

 

[wmn]

One of my neighbors has replaced his twice in 25 years. His dielectric union is so corroded his just unscrews the tank from the bottom of the union. Pokes a small screwdriver to clean out the crude, flushes by turning the whole house water back on for a few seconds into a bucket, then screws on a new tank. His plan is to have it corrected when he replaces the water heater.

 

[wmn]

Is there water in the tank now? I presume yes, and water would come out of the Schrader valve. Also, when you knock on the tank, it should sound hollow. If there is not water in the tank when things are in static stte, it may just be that the existing tank is undersized.

I would not add a nipple in addition to your new valve. I don't know what the thought is on dead legs as it applies to thermal expansion tanks. It seems better to me to not add the nipple plus the new valve. I am not a plumber. I know that my earlier ideas of using a longer pipe to remote the tank is not liked.

Just got brave and checked the schrader valve. Yes, there is water in the tank.