Booster pump for low water pressure

[Alaska]

The municipal water supply only provides 20 Psi at my home (I'm on a hill). I have a holding tank down the hill, 40' lower than the house, and I pump from that tank on up to the house with a separate pump. I run my system at the holding tank at 85/65 Psi with a small bladder pressure tank and it is OK at the house. The municipal supply is from a 2" line and has good volume.

Can I put a booster pump in parallel with the municipal line at the holding tank location and get good pressure at the house? The pumps I see only go to 60 Psi or so and with the 40' lift this would be very marginal. Does the booster pump add to the pressure of the municipal line or does it just increase the volume?

I have posted a better description and a drawing of the existing system and the proposed booster pump.

I have posted a better description and a drawing of the existing system and the proposed booster pump. A link to the picture is here.

http://www.rblantz.com/~pump

Thanks for the help.

 

[electricpete]

From my understanding the drawing represents the existing system.

The in addition to the existing system you want to add another booster pump "in parallel with the municipal line at the holding tank location". I cannot picture exactly where you want to add a pump, but if it is upstream of the bladder than I don't think it will change the pressure to the house. Bladder with associated pump set to 85/65 controls pressure to the house unless perhaps that pump can't keep up and let's pressure drop further. Pressure at house will be approx 20# lower due to elevation, plus an additional amount lower due to pressure drop.

Off-hand I would think that if you want to increase pressure to the house then you need to increase pressure at the bladder (provided it is designed to withstand the higher pressure). It may be as simple as increasing the pressure control setting of existing booster (but that won't work if pressure control is too close to booster pump shutoff head). Or perhaps the new pump should be added in series with existing booster pump and controlled off the same pressure (with higher setpoint).

I'm just thinking out loud here. You need to make sure that whatever you do is safe and doesn't damage your equipment.

Have I understood the proposed addition correctly? Any other comments from the others?

 

[SteveKW]

From what you describe and the location you want to put that Davey, it will work just fine. Confirm from Davey that the pump will be ok with the existing bladder tank after it and at what pressure the tank should be set at.

 

[Alaska]

Thanks for the input. There is no booster pump installed yet. The one shown on the drawing is the "proposed" pump to be installed and the location it will be installed

 

[Cormoran]

Your water supplier maybe don´t accept one pump pumping in his line. Consult with him. Several don´t.
If line is dry, what happen with the pump?

 

[stressriser]

Cormoram has a point, taken in understanding that booster pumps can not be running alone. Pressure and flow must be present before the booster pump kicks on.

If you can find a way to insure this, you will have an increase in flow and pressure from the booster pump.

 

[boo1]

A booster pump, is used to increase the water pressure of water that is already on its way somewhere. You have a system that needs 70 PSI of pressure to operate. But the water line coming onto your property only has 20 PSI of pressure. In this cases you would install a 50 psi booster pump to raise the pressure from 20 PSI up to 70 PSI for your system. So to put it another way, a booster pump is used to "boost" the water pressure. Almost all booster pumps are the "end-suction centrifugal" type.

The total system pressure will be the municipal supply pressure + max pump boost pressure. Pumping through long runs of piping or elevated requires more pressure than flat sites or compact plumbing systems. The water level is not just 40 feet above the house there is also 400 feet of pipe between the tank and the house! The answer is that distance does not matter when the water is static (not moving) in the pipes. Because the water is a non-compressible liquid it transfers the pressure horizontally along the pipe route for pretty much any distance without any lose of pressure! If we measured the pressure with the water flowing the pressure would be termed "dynamic pressure". With the water in a dynamic state (flowing in the pipe) the water would loose pressure due to friction on the sides of the pipe and we would get a lower pressure reading at the house. But static pressure means no flow, no friction, and no pressure loss! Estimate your flow (GPM) and pressure (feet of head) requirements and select a preliminary pump model to use.

The ground level is 40 feet below the water level in the tank. Therefore the water pressure at ground level is 40 feet of head, or about 17 PSI. The line pressure loss is a function of line size (2&quot, type, and flow.

Therefore the required booster pump pressure is simply the desired pressure minus the existing pressure. Just remember the pressures must be expressed in feet of head, not PSI!

PSI x 2.31 = feet head

So in conclusion it will work and supply your house with 40 to 45 psi water pressure.

 

[stressriser]

Something electricpete said triggered a thought that I just can not shake out of my feeble mind.

If your bladder tank is by the pump, and down stream from the house, it is only going to measure the pressure at the bottom of the hill. Since your demand is at the top of the hill, don't you want a pressure sensing device up there? Better yet, a tank at the house?

 

[Alaska]

Thanks B001 and stressriser for the explanation. I will now order the Davey pump and I think it will fill my need.

I would like to put a pump and tank at the house but the feed outside the house is split into two sources before it enters the building. So, I have to keep the system pretty much as is ... (I bought the house this way) and I'm stuck with leaving the equipment down the hill at a common point.

Thanks again to all for the input ... I don't want to make an expensive mistake!!

 

[SteveKW]

Stressriser
Water hammer can be a big problem if you put the tank and switch too far from the pump.

 

[ChasBean1]

You're idea is fine. I would put this pump at the house or halfway up the hill, however, downstream of the expansion tank. Halfway up the hill would be better to avoid pump NPSH problems due to low suction pressure. In the drawing, I'm assuming the check valve in the main line between the suction and discharge of the proposed booster is drawn backward? Anyway, you're on the right track. Cheers, -CB.