Pool filter stops working on backwash

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  #1  
Old 05-28-10, 12:50 PM
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Pool filter stops working on backwash

Never had this happen before, but I'm relatively new to pools so not sure if it's just me or what.

Have a sand filter and a 1.5HP Hayward pump. Normally once a week or so I'll backwash the filter to clear out the junk that's built up in the filter.

Every other year I take the filter apart and clean out and 'chunks' that have formed in the sand.

The last time I cleaned it was last week. As of two days ago, after having worked flawlessly for a few years, the pump will no longer work when backwashing.

The backwash process starts, and runs for about 7-10 seconds, then suddenly loses all suction and no longer backwashes anything.

Any ideas on where I should start looking to fix the problem?

The pump will work fine in normal circulation mode.

It doesn't work in the "rinse" mode though, similar to the backwash mode.
 
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  #2  
Old 05-28-10, 03:03 PM
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Ah geez, sounds like you stay current on all the maintainance items that your aware of. So this one might be a tuffy.

Any ideas on where I should start looking to fix the problem?
When you loose backwash is the strainer pot still full?
 
  #3  
Old 05-28-10, 06:04 PM
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Does it loose prime and fill pump strainer with air? Is there pressure in the filter? And you say in the filter position it circulates properly? What model filter is it?
 
  #4  
Old 05-28-10, 09:55 PM
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Originally Posted by mickblock
When you lose backwash is the strainer pot still full?
No, when I lose pressure on the backwash process, the pump strainer is sucking air. If I leave it in that position, it will pump a very slow trickle of water into the strainer area. Eventually if I leave it there long enough, it seems to stop pumping water at all.

However, if I switch the pump from backwash mode back to normal filtering mode, the suction starts up again, and within 30 seconds or so the pump is back to running at full capacity and the strainer hopper is full of water again.

Originally Posted by todrut
Does it loose prime and fill pump strainer with air? Is there pressure in the filter? And you say in the filter position it circulates properly? What model filter is it?
1. Correct, see the above for the full answer.

2. Correct, and switching it back to the normal filter position will fix the issue of air in the system every time.

3. Nevermind

Edit:

Ok, so in the process of going outside to answer todrut's third question, I decided to go through my normal cleaning routine to see if I could get a better handle on where the problem was coming from.

And I figured out the problem. Figure I'll put what I found here so anyone else who might have the same problem can find what worked for me.

So in my case, I went out there to clean out the filter on the pool vacuum. This time, being 20' away from the pump when it happened, I suddenly heard the sound of water rushing into the surface skimmer/inlet.

There was a chlorine tablet wedged underneath the door, which was propping it up. When the filter was in normal mode, the screen on the vacuum had enough debris in it to require less water on the inbound side. Removing that debris meant the normal circulation mode suddenly was using as much water as the backwash mode, and I could suddenly hear water pouring down a hole, instead of the surface skimmer inlet being full.

I removed the chlorine tablet from beneath the surface skimmer door, water came pouring in and life is good again.

Great board though, and thanks for trying to help out.
 
  #5  
Old 05-29-10, 06:55 AM
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Great to hear, however it is very bad to put chlorine in skimmers, it put chlorine at a very ppm going through your equipment which will in time reduce the life of equipment. It is best to install a automatic feeder or at least use a chlorine floater. Just a FYI....
 
  #6  
Old 05-29-10, 07:52 AM
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What he said. Plus when the water isn't circulating that tablet is creating an intense concentration of chlorine inside your skimmer. The materials that make up your skimmer aren't immune to the effect of acid oxidation.

It can also block the function of the door causing flow problems when.... Oh wait you already know that!
 
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