Water Accumulator Tank

[AFChap]

I need an "expert" on accumulator tanks (I'm sure I will find several here !! )

My coach came with an accumulator tank. I paid some attention to it the first year or so and then forgot about it, mostly because of the way it is installed it is difficult to check the air pressure. Recently I decided to pay attention to it again. It was waterlogged, so I turned all water supplies off and opened some faucets and applied air to the tank and got the water forced out. Then, per my owner manual, I pre-pressurized the tank to 20psi. Then I closed the open faucets and turned the water pump on. When the water pump shut down I check the air pressure in the accumulator tank and found it at 90+psi! I reduced it into the 40's, but when I went below that there was no air pressure left. That makes sense to me becuase my ShurFlo 5.7 pump is putting out probably 45-50psi. But the accumulator tank instructions tell me it should have 20psi air pressure ...it does NOT say that is without any water in the system, but it appears that may be what it really means.

So, how about it experts? ...should my accumulator tank show 20psi air pressure with no water in the system, and ?? when the system is pressurized with water pump or shore water?

[a k]

You only air it up when its empty. Usually 2LBS lower then the water pump cut in. It's a cushion so your pump doesn't bang on and off. 90lbs is how much water pressure you have. Kind of high. Usually a house with a well pump runs 35lbs cut-in and 55Lbs cut out

Also with a water logged storage tank, when you heat the water and it expands and is probably why it got to 90 lbs. If not, your pump cutout is screwed up.

[dieselclacker]

Paul 20 pounds pump off sounds about right. Don't know exactly how yours is plumbed, but accumulator tank should be the first thing after the Shur-flow. City water pressure should have no effect on the pressure in the tank, as a check valve closes off that section of the water supply when you connect to the city pressure. 90 pounds is really high for either pressure source. I would disconnect from outside water, and with the Shur-flo off, pressurize the tank to 20 pounds with air. Then turn on the pump and let it run till it shuts off, then check the pressure again, this should be your pump operating pressure. If it is too high, adjust the pump pressure if possible.

Dieselclacker

[EngineerMike]

Paul- I sell the compact Shurflo accumulator which comes factory charged to 20psi (i.e. right out of the box, er, bag, and not hooked up to any plumbing). It has a max rating of 40psi dry. Too much and you will blow the bladder in the accumulator. I see no reason to send it over 30psi dry.

The mounting place in the system should not matter. I recommend a place and orientation where it will be free draining when the piping is drained for winter, otherwise you will find the leak when it ruptures and the ice melts. I have mine mounted up above any plumbing in the basement (mounted to the basement ceiling). House plumbing is above it. The reason location does not matter (assumes open piping, no dead ends closed off by check valves where the pump works without engaging the accumulator) is that the whole of the pressurized plumbing acts like a pressure vessel, same pressure everywhere (ok, within a small amount to account for elevation). If the accumulator is connected to the same pressure regime as the rest of the piping, it all sees the same pressure & same reactions from the pump. The accumulator acts as a sort of long-stroke shock absorber for the pump.

The 5.7's say they don't need an accumulator, but real experience shows that many rigs' plumbing generates a surging effect from the SmartSensor in the 5.7 (mine did). The feedback it is interpreting makes the pump surge for whatever silly reason. Adding the accumulator usually fixes that (mine did).

As to the 20 psi, that's the pre-charge to keep the bladder full enough of air to work. Once you kick on the pump and it goes to 60 or 65psi, the bladder will get squeezed and the bladder air should read same as the wet side of the plumbing.

If your accumulator is hard to reach to check or correct air pressure, add an extender line, plumbed to a place you can put an air chuck or bicycle pump easily. Simple tubing w/a Schraeder valve on the business end will do it (might have to remove the OEM valve stem @ the accumulator nipple unless you use a spin-on end that depresses it for you to add your extender line).