Piscinayspa's advice
Given our experience in pool construction and maintenance, we have found that a domestic filter (up to 750 ø) will always filter better with grade 1.
If the filter is 750 ø it is not compulsory but it is advisable to make the layers with grade 1 and 2.
From 750 ø onwards, the different layers should be made with grade 1, 2 or 3 depending on the size of the filter and needs.
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