Sand filter draining water when pump shuts off

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Weston

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Jul 25, 2010
12
I have a 1.5hp Hayward pump and a Triton sand filter. The sand filter is pretty big and has the clear bubble and pressure gauge on top so you can see the water in it. I just recently noticed that all the water in the sand filter is draining when the pump shuts off. When the pump turns on it has to go through the process of filling the sand filter back up with water. When it gets filled up (usually 2 to 3 hours) everything runs fine untill the pump shuts off. Then the water drains again.

Here's the crazy part. I don't know where the water is draining. I've checked everywhere (all around the pump and sand filter, backwash line). The only thing I can think is the water is draining back into the pool. I can hear it draining in the pipes. It is making a chugging sound.

The pump seems fine. The basket right before the pump is holding water and pressure just fine. Even when the pump is stopped.

I'm at a loss. Any ideas would be greatly appreciated.

Weston

1.5hp Hayward Pump
Triton Sand filter
18,000 gallon
Plaster
 
That means you have a leak somewhere. The leak is allowing air into the system when the pump is off, so that the water can drain back into the pool. If the leak is on the suction side of the plumbing you should see air bubbles coming into the pump strainer basket. If the leak is on the pressure side and above ground, you will see a water leak when the pump is running.

One common place to look is the pump strainer basket lid. If that is not properly sealed it can let air in, especially when the pump is off.
 
If it is the pump strainer basket lid wouldn't the basket drain water too?

The whole suction side of the system seems fine. When the pump starts running it looks like everything is fine.

Could it be a leak underground? Even though I am not losing any water in the pool?

It seems like it is after the pump somewhere. Could it be the five way valve thing where I change it to backwash and all that?
 
Jason,

Thanks for all the information. One more question for you.

Does it make sense that sand filter is filling back up and everything is running fine after about 2 hours? If air is getting into the system shouldn't it be getting in there when it's running?

The pool is in the ground. so the pump and the filter are above the pool.
 
Chances are the leak is on the pressure side, or you would be seeing air in the pump strainer basket when the pump is running Your filter appears to have an automatic air vent of some kind (some do, some don't). When the pump is running the filter is letting the air out (all be it slowly). There is still a small chance the leak is on the pressure side. It would need to be a very small leak in that case, letting air in slowly enough that the filter can vent faster than air gets in. But overall it is sounding like a pressure side leak.

Air gets through small holes much more easily than water does. A tiny water leak can make a fairly large air leak.
 
If the pump strainer basket is remaining full, then the leak is on the pressure side.

Have you looked at your multi-port valve? It seems to me like a damaged spider gasket leaking to "waste" would cause that condition. Can you see where the water exits the "waste" pipe?
 
I checked the waste pipe and found just a little bit of water. Nothing major. Of course a little bit may be all it needs.

My multi-port valve is not in the best of shape. If it is the gasket is that something hard to replace? Can I do that?
 
The multi-port valve (I have never done it) is reportedly not too much trouble to replace and certainly a DIY project if you are reasonably handy.

I forgot to ask.....Do you have any check valves on your system?
 
No check valves that I know of. The last thing I did before I noticed the issue was I vaccuumed to waste.

The only other thing I know of is the little looking glass when you backwash. I don't know of any other valves. I have one right before the pump that I switch btwn skimmer and drain. But that is before the pump.
 

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Hmmmm, puzzling.

I can hear it draining in the pipes. It is making a chugging sound.
Click to expand...
Tell us which pipe that is. Sometimes you can feel it with your hand on the pipe. I think that may help identify what's going on.

Confirm once again that the pump strainer basket is staying full when the pump is off.
 
Pump strainer basket is for sure full. No doubt.

I can't be certain which pipes are draining. It sounds like all of them to be honest. I try to feel them and it feels like the waste one and the one that goes back into the pool. I don't see anything coming out of the waste and I don't really notice any activity in the pool.

It's got to be the multi-port valve thing. I just can't understand where else it would be unless it is underground. But if it was underground wouldn't I lose some pool water?
 
Yes, the pool would lose some water even if the leak was above ground. But, as I said above, it only takes a very small leak to let in enough air to drain the filter. Air goes through a hole much more easily than water. So the amount of water lost might be small enough that you aren't noticing.
 
ok. let's say the leak is coming from the multi-port valve somewhere. If it is a small leak will that cause most of the water from the sand filter to drain back in to the pool and maybe just a little out the waste line?

I do keep seeing just a little water coming out the waste line. It is very little.

I think I'm going to attempt to take apart the multi port valve. I'm not that handy but I figure it's just screws.
 
Leaks in the multi-port valve are almost always caused by some problem with the spider gasket. Make sure the spider gasket is flat, firmly attaches, and not nicked or gouged. If there are any problems with the spider gasket you will need to replace the whole gasket.
 
My multi-port is a Hayward SP-710. If that means anything.

I've attached a photo of my setup. Can't attach bc of file limit. I got it figured out.

Let me ask this one last question then I will try my fix. Could the spider gasket (or leak in the multi-port) be causing my sand filter to drain water?
 

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My pump (and sand filter) would always drain with the pump off, even with isolation valves closed and multiport set to close. I replaced the 20+ year-old spider gasket and completely cured the drain (now I can use a pump timer). This could be your problem.

Changing the gasket should be quite straight-forward. Set the multiport valve to a half-way (lifted) position, undo the six bolts on the top section (don't lose the nuts), pull off, cleanout the old gasket, dry the seating, a few drops of superglue to the gasket base, fit gasket making sure it is fully seated, replace multiport top, set valve to filter. There might be slight variances in your particular multiport. You could also change the spring and washers in the port lever and the large o-ring whilst you're at it, and put a little silicon grease on the lever spindle, but that's a little more awkward.

Oh yes, turn the pump off first.
 
It's just that the spring loading will tend to twist the top of the valve up when you are unbolting it - and ditto when you are reassembling it, and could damage the housing or fittings. To avoid this put the lever halfway between any two adjacent settings so that the spring pressure is taken off the gasket seating.
 
Just wanted to give a heads up. I replaced the whole multi port valve (the top part), put in a new spider gasket and the other little thin gasket around the top.

The spring on my multi-port was shot and was over all in bad condition. So was the spider gasket.

It took a little elbow grease to get the spider gasket out but once I got it started it was no problem.

Now everything works like a charm. At the expense of about $110.

I'm not the greatest DIY type of guy but I'd have to admit this was fairly simple.

I appreciate all the advice and help. Sorry for the late response.

I hope this helps someone like me in the future.
 

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