Dirt coming through the returns

Hello all, I've had an issue all season with dirt coming back in though my returns. It's actually too heavy for my vacuum to pick up so I have to brush it into one spot and then scoop it with a bucket. It's not an insane amount of dirt, but over the course of a week or so it adds up. It only comes when I run the filter. Seems like it's coming out of both returns. I'm not losing a lot of water in the pool although I may be losing some more than is normal. I've had to use a hose to add water once this season, but it was after a very hot sunny two weeks and lots of use. Anyway, I don't see any air in the pump, but when I turn it off it does slowly get air in it. Does it seem like the dirt would be coming from a broken pipe or a filter issue? I have someone coming tomorrow to look at it, but I'd like to have an idea of what it could be first.

Any thought?

I have a sand filter that I changed the sand on 4 or 5 years ago. The water is clear. Everything else seems to be running normal. TIA

Thanks

Jon

What you describe is very, very strong indication of missing sand.

This is commonly a result of matching an undersized sand filter with an oversized pump, which results in blowing sand out with every backwash. Unfortunately, this pairing is common, because oversize pumps are 'sexy' (BIG horsepower!!) and don't cost much more than smaller pumps, whereas nobody gets excited at sales-time about a 30" filter instead of a 24" filter.

Verification test? Go to Walmart, etc and buy some DE filter powder. Add a few cups to the skimmer when the pump is on. If a white stream emerges from the returns . . . you've verified non-filtration, which is almost always lack of sand.

Short term solution? Add more sand.

Long term solution? Either get a bigger filter, a smaller pump OR replace the impeller on the existing pump with a lower HP rated impeller. (You can put a small impeller on the same model pump, so long as the HP of the MOTOR is higher than the HP rating of the impeller. BUT, if you put a big impeller on a small HP motor . . . you'll just burn out the motor. Job requires some skill, as well as a new impeller and seal. It's prudent to ALSO plan on replacing all case gaskets & O-rings.)

Alternative kludgey solution? Install a valve on the EFFLUENT side of the pump, BETWEEN the pump and filter, and throttle maximum flow to less than 15 GPM per sft of sand surface.