Accumulator - another pressure question

[Marv_Hoag]

My 2000 Monaco has a accumulator tank in the water system. Does the tank control or regulate the pressure when using the pump, or is it a pass through that delivers whatever pressure the pump delivers.

I want to install a 55 psi pump but have no idea if the accumulator tank can stay or has to be removed to achieve the higher pressure.

[wa8yxm]

Marv Hoag wrote:
My 2000 Monaco has a accumulator tank in the water system. Does the tank control or regulate the pressure when using the pump, or is it a pass through that delivers whatever pressure the pump delivers.

I want to install a 55 psi pump but have no idea if the accumulator tank can stay or has to be removed to achieve the higher pressure.

Option 2, it is nothing more than a tank, or bottle with a single in/out port (ok it may be a bit more complex internally but functionally that is all it is)

As the pump pushes water into the tank air (or a spring but usually air) is compressed, When the pump shuts off the tank "Delivers" water, initally at the pressure the pump shut off at, but quickly dropping till the pump kicks back in.

The function of the tank is to REDUCE the number of pump cycles (It also lengthens them) it has no regulation ability and does not reduce total pump run time.. but it may make a slight improvement in power consumption. (Depending on what type pump you have).

[Dutch_12078]

Marv Hoag wrote:
I have installed the revolution water pump and have left the Jabsco accumulator at factory pressure of 20 psi. Everything seems to be functioning.

With the higher pressure pump (55psi)should I increase the pressure in the accumulator to 30 or more psi, or leave it as is?

The controlling factor for the accumulator static pressure setting is the cut-in point of the pump, not the cut-out at the high end. If the system is functioning to your satisfaction, I'd say leave it alone. Otherwise, you might be able to tweak the tank pressure a bit to increase the draw down slightly. Or not...

[adondo]

Marv Hoag wrote:
...Everything seems to be functioning.

As Yoda from the Star Wars series would say:

"Mess with it, you shall not." :B

Like the old adage says: "If it's working, don't touch it."

[Marv_Hoag]

I have installed the revolution water pump and have left the Jabsco accumulator at factory pressure of 20 psi. Everything seems to be functioning.

With the higher pressure pump (55psi)should I increase the pressure in the accumulator to 30 or more psi, or leave it as is?

[Old-Biscuit]

The Shurflo Revolution Pump is NOT a variable speed pump.
It runs at speed on demand and discharge pressure is controlled via an internal bypass valve......bypass starts opening at 35 psi and is fully open at 55 psi.
This reduces pump on/off cycling and helps maintain a more constant flow.


The Extreme Series Pumps are variable speed and use a circuit board and microprocessor.

[JimM68]

as Alondo said, an accumulater is not recommended with a variable speed pump.

We use a shurflo extreme, no accumulator, it works great.

[adondo]

I guess I should've talked about pumps too. 🙂 I didn't know you'd upgraded pumps. :B

The older pumps run at 100% speed and have a pressure switch. There's some hysteresis there, just like a thermostat in a house. You don't want the pump to be going on/off/on/off/on/off/on/off/on/off/on/off, so the switch has a few lbs. of difference between starting the pump and allowing it to drop pressure just like your furnace doesn't turn instantly on/off the same way. (Usually 2 or so degrees in the T-stat) The pressure difference can be 10~15 PSI or so, and that makes for a pulsing flow, and a chattering pump depending on what level of flow.

Now, the NEW pumps (The better ones) are microprocessor controlled with a solid state pressure sensor. Those will run the pump motor at anything from 5% to 100% speed depending on water flow. They maintain the pressure at an even amount, (close tolerance) and just speed up/slow down to keep up with demands from an open faucet as you turn the valve.

An accumulator won't hurt anything, but it's just redundant with a variable speed pump. The pump may even run a little oddly to maintain its set pressure against the tank's air bladder because there's no binary on/off switching going on.

[Marv_Hoag]

Don't know why I didn't do this in the first place. Called Shurflo tech support. Here is what they recommended. The Revolution series pumps are designed to work without a accumulator. I can either drain the pressure and let it work as a pass through or take it out.

Time to take another look at the plumbing. When the new pump arrives, part of the install will be to first raise the accumulator pressure from 20 to 30 psi and see how it works. If I'm not happy with the performance I'll bypass the accumulator tank completely and remove the tank.

Thanks again for the comments and help.

[Dutch_12078]

The Revolution pump works fine with a 2 gallon accumulator tank. The pump cut-in pressure is about 30 PSI, and the cut-out is the expected 55 PSI with the factory settings, very similar to a standard residential pump setup. About the only difference I've noted with Revolution/accumulator installations is that the pump tends to run a bit longer as the tank pressurizes and the pump bypass valve starts to open before reaching the rated 55 PSI. The run time could likely be adjusted down a bit by raising the bypass pressure, but I don't think that's really needed.

[gatorcq]

Pex water system have been rated for well over 100psi, and can handle temperature range from freezing to well over 150 degrees. Susan and I are certified Pex system installers (built own 3000 + sq ft house). One of the test for Pex is heating it up with a torch and shaping it. RV manufactures pressure test their system to 80 psi.

[bluebirdPT36]

Goulds (well pump systems) says to precharge tanks 2 to 3 psi lower than pump cut-in pressure. This is with no pressure on the water side. This gives maximun drawdown.

[Chris_F]

Mary,

I'm not sure if the ShurFlo pump system will work the way you want.

For background, a typical well pump system uses a pump, a pressure tank (accumulator tank), and a pressure switch.

The pressure switch controls the pressure. These days, the switch typically is set to turn the pump on when the pressure in the tank drops to 30-40 psi, and turns the pump off when the pressure reaches 50-60 psi.

The air pressure in the tank does NOT control the water pressure. It only acts as a cushion to push against the water pressure. Typical air pressure is 5-10 psi with no water in the tank.

The typical well pump flow rate is 7 gpm or higher as needed to meet maximum flow demand. The flow is measured over the pressure range set by the pressure switch.

Now let's look at your proposed system. The switch on the ShurFlo pump appears to shut off the pump when the outlet pressure reaches 55 psi. There is no indication that the pump will start at some lower pressure, so it looks like it will start back up when you lower the pressure by opening a faucet. That's why the pump instructions say a pressure tank is not needed.

The stated volume of most pressure tanks in considerably higher than what it will deliver to service. For a 2-gallon pressure tank, the "drawdown volume" from 55 psi to 40 psi likely will be in the range of 1/2- to 3/4-gallon.

I visited the ShurFlo pump site and downloaded the pump pressure curve, which indicates the flow rate vs. outlet pressure. The rated flow of 3 gpm is delivered only when there is no pressure at the outlet. At a discharge pressure of 40 psi, the flow drops to 1.2 gpm, and at 55 psi it drops to about 0.25 gpm.

What does all this technical stuff mean to you? Let's say you want to take a shower and the low-flow showerhead delivers 1.25 gpm. When you open the faucet, the ShurFlo pump should start and deliver water at the rate of 0.25 gpm. To keep up with the shower flow, water will flow at the rate of 1 gpm from the tank. After about a minute or two, the pressure will have dropped to 40 psi. At that pressure, the pump output will have increased to 1.2 gpm, so the pressure won't drop much more.

ShurFlo makes good pumps, and I know a lot of people who are very satisfied with them. However, it doesn't look like the accumulator tank will prevent pump cycling, and the only way to predict if it will deliver more water is to look at the performance curve for your current pump.

[Marv_Hoag]

Thanks for all the information. My accumulator holds 2 gallons. I just ordered a new Sure Flo revolution pump which is OK to use with accumulator. Plumbing will have no problem with 55 lbs.

Will be happy when the 40 psi pump is replaced.

[Old-Biscuit]

Check whether or NOT that your pump style/design can be used with an accumulator tank!! Accumulator tanks are not recommended for use with some newer pumps.
Go to MFG. website and verify.

55 psi is not going to be a problem with your rig plumbing lines/fittings....
(unless you have really junk plumbing)