When I'm using my water hose, especially with the electric pressure washer, after about 15 minutes of use, the water pressure drops. I can disconnect the water hose from the pressure washer and although the hose is running full, it has a very weak stream. This isn't a problem in the house and we never notice it, even when the washer is running or if we are taking showers. I have no water leaks anywhere and this problem is present even if I'm just using the water hose without the pressure washer. My water system is residential. I have a 4" well with a submerged pump and a pressure tank in the garage. The system is four years old.

Would this be a pressure switch problem or a pump problem?


Thanks, guys for all the helpful answers. My pressure tank is a 40 gallon and I have not problem running out of water or the pump keeping up. I have ran four hoses at the same time watering apple trees and landscaping almost all day as well as our in house use without any problems.

Actually, I have since found the problem. I should have read the instructions to the pressure washer more carefully as it specified not to use more than a 25ft. hose connecting it to the water supply. I just connected to my hose supply which is on a hose real and contains several hundred feet of water hose. Evidently, by the time the water circulated through all those hoses on the real, it was being restricted somewhere along the line. I disonnected one hose and the thing worked like it should. I do need to up the low pressure setting on my pressure switch as I like to have a kick on pressure of 40psi and kick off pressure of 60psi and right now it is a few psi below 40 but other than that things are like they should be.

Thanks again for all your help.

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  • Is the pressure switch in the garage near the tank? – 3264 Aug 12 '11 at 15:46
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    Please consider registering your account. This way you'll retain ownership of your questions even if you log on on a different computer. – ChrisF Aug 15 '11 at 17:16

The part that jumped out at me is this: "4" well with a submerged pump and a pressure tank in the garage."

How big is your pressure tank? My guess is that the greater water draw of a 1/2 or 5/8 inch hose can drain the tank in 15 minutes. The washer or shower has a much lower flow rate in gallons per minute used than a hose.

When the pressure is low from the hose, do you also get low pressure inside the house?

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  • Yeah a 4 inch well is pretty darn shallow. – JohnFx Aug 13 '11 at 23:32
  • I think 4" is the diameter, not the depth... – Karl Katzke Aug 15 '11 at 1:08
  • I'd bet it's a 4' well and not 4" considering it's a submerged pump. Those are used for shallow wells. – Cody C Aug 15 '11 at 13:03
  • @John FX: The 4" is the diameter of the pipe. The well is 125' deep with an abundant depth of water table. – Kenneth James Aug 16 '11 at 13:46

I would believe the pump isn't keeping up with demand and the pressure tank is supplementing it for the first 15 minutes.

Where I live the pump can run at full steam and the pressure tank is used for reducing the number of times the pump turns on and off.

Test - Turn off the pump attach a hose closest to the pump and drain the water tank. Leaving the hose open, turn on the pump. How is the water volume and pressure?

If the pressure is not that good after the test, then the pump itself doesn't put out the flow you need. At that point you could get a bigger tank to extend your 15 minutes.

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@TNT is close, but it is likely that the well itself isn't keeping up with demand (low yield).

The well itself acts as a reservoir, and has water flowing into it from sand and fractures in the rock around it is drilled through. When the pump is off, the well will fill up a certain amount, after which point it will turn off. This is point is called the static head of the well.

The water will flow at a certain rate (which may vary depending on season, and where the water is actually coming from), and so that's the maximum flow rate you will get from your well. The flow rate can also change a bit depending on the amount of water already in the well: sometimes when the level is below a fracture, more water will come in, but when it's above, it won't contribute much.

Your pump itself will also have a maximum flow rate, which depends on the size of pump, motor, head (amount of water above the pump), depth (from the pump to pressure tank) and total distance of pipe. If your well doesn't produce at least this much water, you will be starving the pump for water and running out.

When you first open the tap, the water will come from the pressure tank. As soon as the pressure drops to the cut-in pressure (usually ~40-50psi), the pump turns on and fills the tank up to ~60-70psi. When that happens, it's using water that is sitting in the well. If your well produces less water than your pump, eventually your pump will catch up and now be running dry, or very close to it.

In your situation, it sounds like your well yield is just slightly less than the pump can do, and so the pump is using up the reserve in the well, and then while the pressure drops it's on the edge of running dry (which can be very hard on the pump, btw).

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  • Why the downvote? If I'm wrong about something, please comment. – gregmac Aug 15 '11 at 15:30

You can buy a PRV, pressure reducing valve, from a hardware store to drop your pressure down. The problem with reducing it the way that you are is if the output is reduced the RO unit will get full pressure. I would go and look for a PRV if you want to reduce the pressure, I think that they are less than $10. It works on the same principle as the regulators for air compressors.

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  • How will a pressure reducing valve increase the water pressure? Can you explain your answer a bit more? – Tester101 Nov 13 '12 at 17:29

It appears that you've resolved the problem, but one thing to consider when troubleshooting issues with pressure tanks is the air-space at the top of the pump. Usually there's a tire-inflation valve somewhere near the top of the tank. Connect a bicycle pump to that and pump a bit more air in. The air space acts like a spring, maintaining the pressure. More air is equivalent to a bigger spring.

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