The basis for your clean pool
The filter and pool pump are the basis for obtaining clean filtered water. 
To obtain and keep the water clear and clean it's important that the pool water is pumped through a (sand) filter.
If you would not filter the water, bacteria, algae and fungi get a chance to develop in the pool water and adding products to your pool water is not very useful.

Maintenance of a sand filter
With a sand filter, you must perform a backwash (minimum every three weeks, this can also be more) and after 5 years you must replace the sand from the filter with new sand. If the sand filter has not been circulating for a long time, thesand will start to stick together and you will have to replace the sand.
Besides backwashing and replacing the sand, you should also put superflock plus in your skimmer. 
Superflock plus is a candle-shaped flocculant used in sand filters for effective prevention and removal of turbidity in the water. Due to its patented formula, superflock plus dissolves slowly, which results in a long-term effect. Use superflock weekly for optimum results.

What do you put in a sand filter? 
When the sand filter is delivered, it's always stated what it's recommended to put in the sand filter. You can put sand, glass filter media or flint in the sand filter. Sand and flint come in different sizes. To determine what and how much you should add to the sand filter. It's best to look at the paperwork of the sand filter. Sometimes there is a choice between glass or sand, in which case you can ofcourse choose. 

Working sand filter
In a sand filter, swimming pool water enters the sand filter from above and sinks down through the sand. Because the water sinks down along and between the sand, dirt from the water stays behind with the sand. 
This is how the water is filtered.
Because the water descends via the sand, a lot of dirt remains in the sand after a while. In order to clean the sand, a backwash (rinsing) must be carried out. By performing a backwash (every three weeks), the dirty water is pumped through the backwash and goes to the sewer or to another drain.
After 5 years, you should replace the filter sand with new sand. 
If the sand filter has not been circulating for some time, the sand will start to stick together and you will have to replace the sand as well.
The amount and type of sand to be used is always indicated on the sand filter.

The different settings of a swimming pool sand filter 
There is always a six-way valve on a sand filter. Six-way valve because the sand filter can be operated in six different positions.
Please note: If you change the mode, the pump must always be switched off!
If you don't do this, your pump may be damaged.

1. Filter: Filtering the pool water. The water goes via the pump to the sand filter. The clean, filtered pool water then exits the sand filter into the pool.
2. Waste (empty): This is to drain all the water out of the pool. This is only necessary when the pool is very dirty and needs a thorough cleaning. 
3. Backwash: 'backwash the water'. This is to clean the sand filter. The water goes out in the opposite direction (into the sewer or another place). 
To backwash, you must first turn off the pump! Then first set the 6-way valve to backwash and switch the pump on. The water now flows in the opposite direction. Backwashing takes 1 to 3 minutes. If you look through the sight glass of the sand  filter and the water is clear again, it's sufficient.
4. Rinse: The six-way valve should be set to this position immediately after backwashing. You do this for 30 seconds. In the rinse position,  the water goes from the top to the bottom while it's discharged into the sewerage. This way, all the sand comes back into place.
5. Circulate: This position is to mix certain products with the pool water as quickly as possible. The water is drawn in by the pump, but does not pass through the sand filter. 
6. Closed: Now all outlets are closed. You must now turn off your pump as quickly as possible, because the pressure builds up rapidly. The closed position is mainly used when working on the sand filter.

In short, The 6-way valve is usually on the 'filter' position.

How long should your pool water be filtered for?
The more your water is filtered, the better your water quality. This is very clear. 
But how long should your filter run? 
Well: 
the outside temperature is less than 20°C, let the filter run for 12 hours.
If the outside temperature is more than 20°C, let the filter run for 24 hours.
Tip: Set the filter operating time with a clock, In this way, you can choose to let the filter run at night.