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Water accumulator tank

Hello everyone,

In the course of tearing down my 91 U225, found the accumulator tank (under the couch up front on the driver's side) wasn't mounted very well. Decided to pull it and fabricate a new mount for it. After depressuring everything we pulled it. Having sat for a time, what drained out was very nasty. Also found there was no air charge left on it. Diaphragm had failed. Given it's age, no surprise.

The accumulator tank has a 2 gallon capacity; approximately 1/2 of that is water, and 1/2 compressed air. A diaphragm seperates the two sides. It acts as a buffer, reducing pump cycling considerably. There are two basic types - bladder and diaphragm, the latter being far more durable and reliable.

They are charged with air to 2 psi below the pump pressure setting. After the pump charges the water system, a volume of pressurized water ends up in the accumulator tank. When you open a faucet, the accumulator tank begins to empty. If you only draw a small amount of water, the pump does not run. Once the pressurized water in the accumulator tank empties out far enough, the pump will run to charge it back up.

These are very simple and reliable devices, but like anything mechanical, will fail at some point. I recently did a fair bit of research on accumulator tanks relative to a project I worked on for a client, and thus knew right away what I was dealing with. I had spec'ed the same unit for my client.

A couple of pointers regarding their use - water left in there will begin to stagnate after as little as 24 hours. Always depressurize the water system if not using the coach for awhile. That will empty the accumulator tank.

The manufacturer recommends that the air charge be emptied if the unit remains unpressurized for longer than 30 days. This is to keep the diaphragm from stretching. It is stressed the most when pressurized with air, but without a water charge to balance the pressure. However, given it's location, can't see anyone going there. The type in my coach does not require periodic air recharging, according to the mfr, but it's something I would check annually to make sure.

These have a rated life of 5 years, although usually last longer. If you find you need to replace the accumulator tank, this is the one, and the linked site has best price I could find.  Goulds Pumps HydroPro Water Pressure Tank - DiaphragmType, In-line Models -

Hope this is useful.
Steve
1991 U225 Grand Villa

Re: Water accumulator tank

Reply #1 –

When our tank failed, I opted to go without a replacement and switched to a new variable speed pump.  Happy.  Happy. Happy.
George Stoltz.  Retired from full-time living in a great Foretravel and now are back to living in a traditional sticks and bricks in Florida.

Re: Water accumulator tank

Reply #2 –
Steve, new style water pumps do not need the accumulator to eliminate pulsing on low water flows. Many have been using them and have thrown away the accumulators that have the problems you are familiar with. Sureflo has newer 4008 with an internal valve that is set to bypass at a few psi below switch setting.
Barry & Cindy

Re: Water accumulator tank

Reply #3 –
Does anybody know the make and model of the pressure tank used in 1998 era ft? I want to replace with the same one so I can use the same mounting. My bladder is blown and is annoying me with the variable speed pump. I want to retain the pressure tank for water heater expansion.

A blown bladder wouldn't have mattered much if the tank was mounted vertically with the outlet on the bottom (air rises).
1998 U270 34'

Re: Water accumulator tank

Reply #4 –
Water worker 2 gal. get one for hot water, it has a different bladder.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: Water accumulator tank

Reply #5 –
The one that was in my '99 is a Flo Jet 20799.

Re: Water accumulator tank

Reply #6 –
Follow up. Here are pictures of the new and old. New is slightly shorter, and barely fits in the hose-clamp style mounts...but it works. I used a hot water-heater expansion tank instead of a pressure tank. I think they are the same thing, but who knows. I pumped mine up to 90psi because I have a variable speed pump and it just serves as an expansion tank as the water heater gets hot.

Reused the existing fitting and reused the rubber gasket (in decent shape). I think the new tank was $30-40 at lowes. Old one definitely had a busted bladder as it had water in the air side.

Edit: Let me add that I have a variable speed water pump the comes on and adjust speed according to the flow of water. I enjoy it over the original one speed design that uses accumulator. The variable speed pump is why I pumped it to 90PSI on the bladder.
1998 U270 34'

Re: Water accumulator tank

Reply #7 –
Replaced my water pump last year and added at small tank from ebay.  Let's you turn on the water for short duration without pump coming on. Did not have one before but forum members recommended.  Really is a nice feature. Dan
Dan & Shirley Stansel
2002 U295 4020 AGDS Build#6054
Towing Buick Enclave & M &  G Braking
Emerald Bay, Lake Palestine, Texas
MC# 16650