Oversized Pump for 21' Above Ground pool

Gregc73

Active member
May 14, 2008
26
IL
When I backwash my pool, I usually get sand spitting out of the return for the first few seconds that I turn the pump back to filter mode. I've checked all the pipes in the filter and they all seem to be fine, no cracks or anything. So after doing some research, I think that I probably have a pump that is too strong for my pool. I don't know the HP of the pump off hand (I'm at work), but I know that when I bought the pump and filter combo, I accidentally told the pool guy that I needed it for a 27' foot pool instead of a 21' foot pool. Short of buying a new pump, is there anything I can do about this? Would getting smaller lines help anything or would that just make it pump shoot the water out that much harder? I'd rather not buy a new pump because of this, but cleaning up the sand everytime I backwash is becoming kind of a pain.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
What size pump and what size filter do you have?

Sand coming out of the filter almost always means that the filter is broken, often a cracked lateral.
 

Gregc73

Active member
May 14, 2008
26
IL
I just opened the pool this morning and I checked all the laterals and there are no cracks. Sand just keeps dumping in the pool though every time the filter goes on or off. My pump size is 1HP (so I guess that isn't the problem). I can't find the gallons on the filter, but it is a big one. It says it pumps 25 Gal/min if that helps.

Is it possible I have the wrong size sand in there? it says I should .45-.55 mm sand. Is that standard pool sand? I bought the sand at the pool store, but I don't remember seeing different sizes.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Pool filter sand is the same size world wide. I have heard of one pool store that carried the wrong size sand (too large), but that is quite unusual. Play sand from a yard and garden place will not work, but it won't get out of the filter either, since it is larger than filter sand.

Other problems I have heard of are laterals that were lose in the main pipe, so sand could get through to the main pipe, and main pipes that were made of two pieces that slip fit together loosely enough that sand could get through there. Cracks in the laterals are sometimes difficult to spot and don't need to be very large to let sand through.
 

Gregc73

Active member
May 14, 2008
26
IL
Thanks for the quick reply. I guess what I find strange is that from day 1 since I got this filter, I've had problem with sand getting into the pool. I've already replaced the laterals once and it made no difference. Maybe I just got a bad filter and it's time to replace it.
 

Gregc73

Active member
May 14, 2008
26
IL
Sorry to keep bringing this up, but I'm really trying to get to the bottom of this and I just thought of something else.

One thing I found strange about this particular filter is that the center pipe is not long enough to allow the lateral house to sit all the way to the bottom of the filter. Basically, there is a few inches of sand, then the laterals start. Could this be the problem? Should the pipe be long enough so that the lateral house (sorry if I'm calling it something it isn't) sits on the very bottom of the filter? I'm thinking maybe once it gets under pressure, the whole unit is sliding up and down causing sand to get in. Any thoughts?

I figure I can maybe replace the pipe with a custom fit PVC pipe if you think that might help.