Pump Priming and Check Valves

[Sirecks]

Hello everyone. We have a pool that is down the hill from the pump and filter. There is a check valve currently installed between the pump and the pool. It is actually after the main and skimmer valves, just before the pump itself.

We're having issues where the pump will not prime after periods of rest after being shut off. It seems to be intermittent. I installed a timer and put it to come on around 11 am and shut off around 6 pm. It worked for a few days and then we noticed one day the water wasn't flowing. The pump had lost it's prime. I spent an hour or so trying to prime it. I had to actually put garden hoses down in the skimmers to force water up to the pump to get it to work again. We also noticed we had a few leaks in the plumbing around the filter. We called out a pool guy to come look at the situation and he fixed all the leaks, and recommended running the pump a bit longer, with a short run in the middle to keep the lines full of water.

I then set the timer to come on around 7 am, and shut off around 7 pm, with a one hour "on and off" around 1 am. The first day or two this worked, and seemed to solve our issue. Then, the pump lost its prime again. Just like before. The pool guy we called originally then recommended installing a second check valve to help trap the water in the system to give the pump a prime. I contacted another pool guy for a second opinion and he said that might help, if the check valve is installed after the filter somewhere.

I'm looking to solicit advice from you guys, to see if you think that a second check valve will actually solve this problem. Also, looking for any other ideas you may have regarding the water running back down the hill and draining the lines during periods of not running for a number of hours.

This picture is my set up. The red arrow is the check valve and the blue and green are the main and skimmer valves. I am sorry to insult your intelligence . . . . I was using this picture for something else. I know you guys know this. Sorry.

 

[mknauss]

I assume the system worked for some time and now is having problems. So something changed. When the pump is running and fully primed, are you getting air in the lid of the pump? This would indicate a suction side leak that would assist in allowing the water to drain back with the pump off. The most likely item is the check valve is leaking. Have you taken it apart to see if there is any damage to the flapper or gaskets?

Those are a quick couple items. Others will be along I am sure to give advice.

Take care.

 

[Jimrahbe]

s,

In a well operating system a check valve in front of the pump is just not necessary. Think about how if you put your thumb over the end of a straw and pull the straw out of a glass of water, the water stays in the straw. If you let air back in the water just come out of the bottom of the straw.

The fact that your pump will not stay primed is an indication of an air leak somewhere in the system. Since leaks on the pressure side of the pump usually spray water out, they are generally easy to spot. This is why 95% of priming issue are on the suction side of the pump. That said, it is possible to have a leak on the pressure side where you just can't see any water leaking out.

My guess is that 75% of suction side leaks are because the seal under the pump lid is no good. This can because the O-Ring is bad or just not lubed. The same can be said of the pump drain O-Rings.

I can't tell for sure, if your pump is connected with unions or not. If it is, then those unions have O-Rings that need to be looked at. If not, and the pipe is just threaded into the pump, then that makes a great place for an air leak. If the pump has ever run dry for any length of time and gotten hot, the threads can expand and cause leaks.

I see two valves in front of the pump... Skimmer and Main drain. They can also leak. Rebuild kits are pretty cheap.

One way to find a suction side leak is to turn the pump on and then slowly run water from a garden hose over the various valves and pump plumbing while watching the bubbles in pump basket. You should see a change in the bubbles when the water runs over the leaking area.

I see water all around the pump.. What is that from???

Thanks for posting and good luck with your hunt...

Jim R.

 

[Sirecks]

Thanks guys. We just moved into this house about three months ago. We are learning about this set up as we go along. It is our first pool.

What you are saying about leaks on the suction side makes a lot of sense. I'll have to check for leaks with the garden hose, like you suggested.

No, when the system is operating normally, there are no bubbles. It is solid water under the plexiglass and there are no bubbles coming out into the pool.

It was explained to me that the water will, over time, find its way down the hill to the pool with my set up being the pump is up the hill from the pool. What you are suggesting is that with a completely closed system (no leaks), the water will not drain back down the hill, like in your straw example. Is that correct?

That water around the pump is what was left from my repeated attempts to prime it, before taking that picture. I would open up the pump lid, pour water in, close it back up and the water would just be sucked out and no further draw would happen. It got to a point where I would shut the pump off, open the pump lid, and water would come and fill it up from the filter side. I couldn't add water with the bucket because the basket would fill up with that water, before I had a chance to pour in my bucket water. So priming seemed like a waste of time, because it kept filling itself back up.

 

[Jimrahbe]

S,

The higher your equipment pad is above the pool, the smaller the leak has to be to cause an issue. I'm not sure the pump will stay primed forever, but I would think that if you are running the pump once a day you should not be having an issue.

Installing a check valve, between the filter and the pump might let the pump stay primed and might be easier than trying to find the source of the leak.

Does your waste line go to a sewer or can you see the end of the pipe? Do you have any water coming out of the waste pipe when the pump is running normally?

Thanks,

Jim R.

 

[JamesW]

There’s a wet spot around the pump, which might indicate a leak at the seal.

If the pump has run dry, the seal can overheat and fail. The fittings in and out of the pump can also shrink if they get too hot.

Check the pump basket for shrinkage or warping to indicate excessive heat.