Expansion tank waterlogged

90 psi and a failed expansion tank could lead to a pressure relief valve valve going off or dripping.

Where do you read 90 psi? Plumbing code states 80 psi maximum

OK so the idea of the expansion tank on a DHW system is to allow for water in the potable water piping to expand when the water heater has a tank of cold water (maybe below 60°F) from almost running out of hot water (after a teenaged daughter showers). That tank may have an average water temperature of 70°F when all the taps are closed. Lets say you have a 40 Gallon tank and another 5 gallons of water in the rest of the pipes. When the water heater burner stops heating the water in the tank, the expansion can make that water go from 45 gallons total to 49 gallons total. Where does that extra 4 gallons of water go?

If you have a check valve of any type near your water meter, the expanded water can not flow back to the water main in the street. If your water pipes are full of water and there is no air space at the top of the DHW tank, than Hydraulic pressure will build up, and pressure will go from 90 PSI to 150 PSI in pretty short order, and the relief valve on the DHW Tank will discharge the extra pressure (or maybe 125 PSI)

If you use that expansion tank and the out of the box pressure was set at the factory at 45 PSI, then when you turn on the water feed to the water heater, the 90 PSI cold water will compress that air in the tank to 90 PSI by adding 3 gallons of water to that 5 gallon tank. That means there is only 2 gallon of air left to absorb any expansion. That may not be enough for the 4 gallons that may happen from time to time.

In order to get the full use from the expansion than, your air pressure in the tank when it is not connected to the pressure of the potable water system, should be close to the operating pressure of the system. So turn off the cold water feed valve and open a hot faucet to drop the system pressure or zero or as close as you can get to zero. Measure the air pressure in the tank. If the air pressure is below the operating pressure of the home's cold water pressure, then you need to increase the air pressure in the tank to match the operating pressure of the system.

1. In your case, place a pressure gauge on your system and take a reading. let's say 90 PSI
2. Next, Close the cold water inlet to the home.
3. Open a hot water tap in the home
4. Measure the air pressure in the tank (in your case let's say that it has the factory charge of 45 PSI).
5. With a pump or compressor add pressure to get the tank air pressure to 90 PSI.
6. Close the hot water tap.
7. Open the cold water feed to the home.
8. Check the water pressure in the home. should be 90 PSI.

As far as @pecmsg's comment about the water pressure in your home being a little high, I agree. You should invest in a pressure reducing valve at the inlet to your home. regulate that pressure down to about 60 PSI. That is plenty of pressure for most operations in a residence. You will save on future repairs to fixtures and faucets. If you do get the pressure down, then adjust the expansion tank to 60 PSI pressure also. Remember the air pressure MUST be measures when there is no water pressure in the system.

that just means it lost the air. Now if you got water out of the valve then it was water logged.
shut the main valves

Open faucets

Drop the pressure to zero

Pump the tank up to 90

look into auto shutoff systems. Many times your homeowners ins will cover all if not part of.

That tank is large enough, IF it is pressurized properly.

Although without a backflow device anywhere the tank isn't really doing anything.

My experience is you can tell a waterlogged tank by wiggle or tapping on it. A hollow air filled tank is a few lbs, a water logged one could be 30lbs or more.

If it is starting to sag downward it may be another indication.

It is rare these days not to have a backflow device on your incoming water line., it protects the entire city water systems from contamination.

There should be two flat sides to put a wrench on the plastic drain valve. Try not to put sideways force on it.

If you remove the handle and bonnet nut you have a straight shot at the flats.

A large crescent, channel locks are my choice. A pipe wrench can egg shap the plastic and make it harder to un-screw.

And, yeah they do break occasionally, as the plastic tends to get brittle as it ages. Then it is the hack saw blade trick

Screw the big handle CCW all the way, then turn it CW. There is a left hand thread inside that allows the big handle and stem assembly to come out.

Maybe then you can get a large 6 point, or faucet socket on it. That will help to not distort the plastic. I suspect that is how they install them at the factory.

That is a lot of weight on the pipes. An accident waiting to happen. I never like to see the copper pipes take the weight of an expansion tank, waterlogged or not.

Install something like this with the new tank, or even the current one if it only needs air.

These two items work great when installing an expansion tank and bear all of the weight.

brackets are great as long as they are fastened into a stud, concrete or block wall. Sheetrock anchors will not be adequate.

You don't have much headroom there. You will probably need an anode rod like this one.