Pool Sand Filters: How to Choose the Right Size
The sand filter is the heart of a pool's circulation system: the pump pushes water down through a bed of 0.4–0.8 mm silica sand, the sand holds back the dirt, and clean water returns to the pool. Waterstar filters are filament-wound fibreglass (FRP) vessels made at our factory in Badr City, Egypt. This guide shows how to size one, what to order with it, and when a ready-made filtration unit makes more sense.
Step 1: work out the circulation flow
A residential pool should pass its whole volume through the filter at least once every 8 hours. Divide the pool volume in m³ by 8 to get the minimum flow in m³/h.
Example: a 10 × 5 m pool with an average depth of 1.4 m holds 70 m³, so it needs at least 70 ÷ 8 ≈ 8.8 m³/h. Not sure of the volume? The pool calculator works it out from the pool dimensions.
Step 2: choose the filter
Pick the filter whose rated flow equals or exceeds that figure. Rated flows are given at a filtration rate of 50 m³/h per m² of filter area.
| Filter | Vessel | Rated flow | Suits pools up to (8-hour turnover) |
|---|---|---|---|
| T500-20 | 500 mm (20″) | 10 m³/h | about 80 m³ |
| T600-24 | 600 mm (24″) | 14 m³/h | about 110 m³ |
| T750-30a | 750 mm (30″) | 22 m³/h | about 175 m³ |
| T900-36 | 900 mm (36″) | 32 m³/h | about 255 m³ |
| T1005-42 | 1005 mm (42″) | 43.5 m³/h | about 345 m³ |
Then check it against the pump: the filter's rated flow must not be lower than the flow the pump actually delivers. A 1 HP pump gives about 15 m³/h at typical residential head, which is why our Residential Filtration Set pairs it with the T750-30a. Going one size up is never wrong: water passes through the sand more slowly, filtration is finer and backwashing is needed less often. The pool pump guide explains how to choose the pump.
All top-mount filters are supplied with a 6-way multiport valve: filter, backwash, rinse, waste, recirculate and closed.
Public, hotel and club pools: side-mount filters
Commercial pools use our side-mount filters from 1200 to 2000 mm diameter (working pressure 2.5 bar, test pressure 4 bar, sand bed at least 1 m deep). They are sized at a filtration rate chosen by the pool designer, typically 30, 40 or 50 m³/h per m², according to the bather load and the water-treatment standard that applies, not simply at the maximum.
| Filter | Vessel | Flow at 30 / 40 / 50 m³/h/m² |
|---|---|---|
| WS-1200 | 1200 mm | 34 / 45 / 56.5 m³/h |
| WS-1400 | 1400 mm | 46 / 61.5 / 77 m³/h |
| WS-1600 | 1600 mm | 60 / 80.5 / 100.5 m³/h |
| WS-1800 | 1800 mm | 76 / 101.5 / 127 m³/h |
| WS-2000 | 2000 mm | 94 / 125.5 / 157 m³/h |
Send us the pool dimensions and expected use, and our technical team will size the filters.
Important: filters are delivered without sand
Waterstar filters leave the factory empty. The filter media, silica sand plus a gravel support layer in the commercial filters, is ordered together with the filter. Quantities per filter, in 25 kg bags, with media to BS EN 12904:
| Filter | Silica sand 0.4–0.8 mm | Gravel 1–2 mm |
|---|---|---|
| T500-20 | 100 kg (4 bags) | — |
| T600-24 | 175 kg (7 bags) | — |
| T750-30a | 300 kg (12 bags) | — |
| T900-36 | 525 kg (21 bags) | — |
| T1005-42 | Confirmed by our technical team when you order | |
| WS-1200 | 1375 kg (55 bags) | 300 kg (12 bags) |
| WS-1400 | 1650 kg (66 bags) | 450 kg (18 bags) |
| WS-1600 | 2150 kg (86 bags) | 675 kg (27 bags) |
| WS-1800 | 2800 kg (112 bags) | 750 kg (30 bags) |
| WS-2000 | 3800 kg (152 bags) | 1050 kg (42 bags) |
The gravel is a support layer, not a filtering layer: it keeps the sand off the collector laterals and spreads the backwash water evenly, so it cannot be replaced by a coarser sand. Silica sand 0.4–0.8 mm is available from Waterstar.
Ready-made option: the F-35 filtration unit
Where there is no plant room or no space for site pipework, the F-35 filtration unit is a self-standing fibreglass unit that needs no site piping. It includes a skimmer opening, two water inlets, an 18 W / 12 V underwater light with its transformer, a control panel, a junction box and three ball valves. It is supplied without a pump.
Prices
Each filter's price is shown on its product page. Silica sand and gravel are not included in the filter price. For projects and larger orders, request a quotation.