Troubleshooting A Piston Water Pump

I recently received an email from someone enquiring about a Duro water pump that wouldn’t pump water. Although I replied to her email, I didn’t post it here.

In hindsight, I figured that my reply might be helpful to someone else who is having a similar problem with their cottage water system. Keep in mind, these are only suggestions and god knows if any of it will work.

Here is the original question: “Perhaps you can help, or direct me to a web site, as I’ve been searching and can’t seem to come up with helpful info. I’ve been trying for 3 weeks to get the water running, and finally threw out everything, galvanized tank with air regulator, and figured the pump impeller was shot due to all the rust & crud we found going into the pump from the hose end. Your site seemed to say you are familiar with piston pumps We have done everything on your site about putting in a water system (we are using a water tank My tank is a new 20 gal pre pressurized (red lion).), and are not losing prime, but the pump isn’t pulling water. It is a DURO PISTON PUMP and was told it has been recently “reconditioned”. The pump has an air valve on it, which looks like the thing where you put air into your car tires. I also removed a plug in the top and installed an air gauge. I turned everything off & used a bicycle pump to put in air & the gauge pressure rose. Am I to put air into my pump to make it work? Do you know where I can visit on the web to get instructions or manuals / troubleshooting for this pump?”

Here is my response:
I’m assuming the tank you are referring to has a ‘bladder’ for air, if it has a place to pump it up. Although that can be the problem, and sometimes tricky to get right, I doubt that is your trouble. Without seeing your pump in person (and even if I could) it’s difficult to say definitively what might be wrong but…..that said, here are a few things I can think of off hand.

I assume when you plug the pump into the electrical outlet it comes on, the motor runs, the wheel turns etc.

Check to make sure the belt is snug. Not too tight, but snug and not slipping.

I would disconnect the tank, and by pass it if possible. Try the pump without it. If it pumps water then the tank is probably your problem. If it doesn’t, you’ll know it’s something else.

You also mentioned it had been reconditioned. I suspect that means someone put in one of the kits like the one seen Click Here

They may have done that wrong. If the cups or springs are in wrong, it won’t work. Under the bottom of the pump is a bolt. If you remove it, the bottom will come off, showing you where the kit goes, the leather cups, springs etc.

Make sure they are all in good shape and if you lift the cups they should snap back into place. If not replace them. Put a new gasket on and tighten it all back up, good and snug, but not so tight as to crack the bottom. If it is too loose, water will spray out when the pump is running. This is something that needs doing every few years with an old piston pump.

These old piston pumps will usually pump even if they are leaking. I am wondering if the problem may be as simple as your technique for priming it to get it started. Here is what I do.

First, remove the hose that goes to the water (lake, well etc) from where it attaches to the side of the pump. Fill the hose with water. It should fill right back to the footvalve at the end of the hose in the lake or well. (I assume you have a footvalve)

Reattach the hose to the side of the pump. Tighten it on firmly using a clamp to keep it tightly attached.

In the top of the pump (or somewhere near the top) of the cast iron part, there should be a removable bolt, and hopefully printed beside it the words, “prime here” (It might be where you have screwed in your pressure valve) Shut off the water where it leaves the pump and goes to the tank and the house.

Get yourself a gallon or two of water in a jug. Remove the plug, and turn the pump on. It should start to work, water might even splash out of the hole, but I doubt it at this stage.

Start to pour a slow but steady stream of water into the primer hole. The water will start to gurgle and splash back out. If it does, you know the pump is pumping. When it’s coming out, stop pouring and stick the plug back in and tighten it up quickly.

You will probably get a little wet doing this.

Once it’s tight, slowly open the valve to the tank, you should hear water start to fill up the tank and the pressure on the tank gauge should slowly start to come up. Usually they shut off around 40 or 50 psi. Once it shuts off, the tank is full. Slowly open the valve to the house and let the water enter the system, as the pressure in the tank drops the pump should come back on.

In addition to priming through the primer hole, you can also fill the water supply pipe from the well or lake to the pump with water. I find that helps, particularly with jet pumps.

If you don’t have any leaks, you should be in business.

There are some other things you can check as well. I mentioned the FOOT VALVE If it isn’t working, water will come into the system when the pump is on, but drain back out when the pump shuts off. You lose your prime and the pump won’t pull the water up. The same could happen if the hose going to the water has any leaks, which is quite possible if it is old. Even a tiny pin hole will allow the water to drain out.

Sometimes it is purely trial and error, and keep trying. I know you said it wasn’t losing it’s prime, but I would check that again. Very often, when I encounter stuff like you mention, it seems to be in the priming. When the sun, the stars and moon all line up, you get it right, and you get water.

Of course there are other problems, like the motor being burned out, but you didn’t mention it wasn’t coming on, so I assume it works.

Well….I hope something I said helps you out. I would love to hear from you whether it does or not. If it doesn’t we’ll see if we can come up with something else.

This book might also be of use to anyone with a cottage water system. It’s called Cottage Water Systems: An Out-of-the-City Guide to Pumps, Plumbing, Water Purification, and Privies

10 thoughts on “Troubleshooting A Piston Water Pump”

  1. nnnnnnnnnnnnnnnnnnnnnn Very helpful info for me … Thanks I will try some of your suggestions on my duro.

  2. Great article. I have a Duro Piston pump at the cottage, it’s working OK but the pressure relief valve starts to leak at around 10 PSI. I’ve tried moving the slotted inner spring in and out with no change in results. Can this valve be repaired or replaced?

  3. Hi George, You can still purchase parts for many piston pumps. Are you saying the pressure relief valve opens at 10 psi and “blows off” the water pressure?

  4. Thanks. At the present time, it is now dribbling water at any pressure but not blowing even at 40 PSI.

  5. I have a Duro piston pump
    It is taking almost 8 minutes for the pump to get up to pressure before it shuts off
    The water pressure going into the washing machine is very low and slow,
    We have sand in the toilet tank that we did not have last year
    I have no leaks at the pump on either side
    I HAVE CHECKED THE LINE TO THE LAKE AND IT AND THE FOOTVALVE SEEMS TO BE ok[although the foot valve is attached to an old metal stand that is rusty and there could be pins holes that could allow air to get in……is that a possible cause of my problems/
    Tha tank is old and I’m not sure if it has a bladder but wonder if the sand is coming in from the tank or some pin hole leak out in the lake where the foot valve is attached to the rusty metal stand]
    I have had the pump serviced last year and put a new belt on it this year

  6. John, it is my guess (and it is only a guess) that your foot valve is where the sand is coming into your system. I would check to ensure that the foot valve is not getting too close to the lake bottom or located in an area where the sand/shoreline is disturbed, perhaps from boats or wave action. If your hose has pin holes that will allow water to drain back out. I doubt it is or your pump would either lose prime all together or at the very least be running frequently as the pressure drops. If it is doing either of those things, check to make sure the valve is opening and closing properly. You didn’t say how old your pump tank is, but if it is older it probably does not have a bladder. If you had it serviced last year I suspect they would have replace the “leathers” in the pump. Your lack of water pressure and long duration to shut off sounds to me like a leak somewhere in the system, either at the foot valve or in the hose or between the pump and the washing machine. I would likely replace the foot valve and ensure it is not located close to the bottom of the lake/well or in a place with a lot of turbulence. Go over the hose inch by inch for water or if it is old, you could try replacing it. Swap with a neighbor if you can to see if it is the hose before you buy one if cost is a factor. And lastly, go over your waterlines inside and out of the cottage to ensure there is not leak somewhere.

  7. I have an old McDougall piston pump system at home in the country. It has had repairs in the past but I discovered oil all around the pump and outside the pump house. I can’t find any research on these pumps and wondering if it broke a seal or if I’m Jed Clampett today. I figure the former but can you help me understand!

  8. I am not sure what to tell you, sounds like the crankcase has a crack or a seal worn out. I’m not familar with McDougall pumps but according to their website Pompco has some parts for McDougall pumps. Well, they have repair kits for piston pumps including McDougall. A piston pump can always do wit new leathers and gaskets. However, before doing that I would inspect it carefully for cracks in the housing or around the fittings etc. Running it with a piece of newspaper underneath may help to show where the oil is coming from. Pompco’s website is here:

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