Filter gravel is one of the three filter media needed for pool water filtration. The filter gravel must always be placed at the bottom of the sand filter, meaning that it is the first medium to be poured into the sand filter.
If you have a Triton TR40 filter, you should add one 25 kg bag.
If you are using a TR60, you add 50 kg of filter gravel (= 2 bags).
If you have a Triton TR100 filter system, you should add 100 kg or 4 bags of filter gravel.
After adding the filter gravel, you should first add filter sand with grain size 0.4 to 0.8 mm.