There are a number of varying opinions for and against changing sand in a sand filter. There are a few important things to consider before changing sand:
- How often is sand changed on a beach? Sand is a form of glass. It does not rot, it does not degrade but it may wear after millions of years of washing.
- How old is your filter? Older filters, especially those which are sealed by a large number of bolts around the valves or connections, may be difficult to adequately seal after you have re-assembled them. You may also have difficulty finding parts if you break any internals, like the laterals, when you change the sand.
- Foreign media? It may be necessary to change the sand (maybe only partly) in situations where media like concrete dust, or dog hair has clogged the filter, due to activities around or in the pool. It can be an idea to remove the top and scoop off any lint accumulated on top of the sand and stir the sand up if your filter does not appear to be backwashing properly.
- Will it filter finer? NO. A new sand filter does not filter very finely because the sand is clean. Over the years the sand in your filter will settle, accumulate dust and lint and naturally filter finer. A new sand filter is very poor in it’s filtration quality.
- Zeolite versus sand? The sand used in new filters contains granules from 1.18mm-6mm in size. Zeolite has granules from 0.5mm-2mm in size which theoretically gives it finer filtration. So that the filter operates at the same pressure we use less zeolite than we would sand in the filter. The sand we use today is finer that what was used 10-15 years ago so there is not a significant difference and is still the most common filter media. Traditionally sand filters used -1 grade sand which has very large particles. Today Davey recommend 16/30 grade sand which is very fine.
In most cases, we do not recommend changing sand just because your filter is a few years old. Those with older stainless steel filters should not change the sand, due to a lack of available parts for repair. We are more likely to recommend replacing a filter before we will recommend replacing the sand.