Sand Filter not working

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My Pool: About 35 cu.mtrs. Deck level. Sand filter.
Location: Spain

Sand Filter not working

Postby Ingajohn » Thu 28 Oct, 2010 11:05

I am really puzzled. For no apparent reason my sand filter appears not to be filtering anymore. I do not get any pressure build up on the meter - well to be honest, very little. As I am vacuuming I clearly see dirt coming out of the jets. The control valve is working perfectly (I think) - just one year old - I did a sand filter change and major refurb on the pool channel about a year ago.

I cannot think what the problem can be. Someone mentioned thar sand can get "worm holes" that short circuit the water . .

Any ideas . . . ? :cry:

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Location: Spain

Sand Filter not working

Postby SPMG » Wed 08 Jun, 2011 11:08


It is likely that there is little or no sand in the filter.
This could have been caused by a new pump pushing sand out to the drains when backwashing if the replacement pump is too powerful for the filter.
Open the lid of the filter and check the level

Note: The filter and pump are balanced together and their size is determined by the volume of water in the pool. The pump should pass the entire volume of the water through the filter in 4 hours. This is called the changeover period and should happen twice every 24 hours.

A correctly sized pump and filter will sort out the sand level when the filter is newly-filled.

If the pump is too small, too little water will be passed through the filter with the result that the pool goes cloudy.

If the pump is too big then filtered material will be forced through the sand and return to the pool via the jets and also, during a backwash, the sand will be pumped out with the waste water which makes the problem worse. One sure sign of this is grains of sand in the sight-glass on the side of the multi-port valve.

You can see a schematic view of a filter here - ... filter.pdf

Hope this helped


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