Seasonal Pool Care /
How to Winterize a Pool Sand Filter
Winterize a pool sand filter by shutting the system down, draining the tank and plumbing, and protecting it from freeze damage before cold weather arrives.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Sep 13, 2025 so the blog reads as an organized archive. It was not published on that date.
Winterizing a pool sand filter
The process is straightforward: you shut down the system, give the filter a good cleaning, drain the tank and adjacent plumbing of any water, and put in place some protection against the cold. Of course, there are nuances depending on your particular pump, valve and filter configuration, so the manufacturer’s manual for your model should be your guide.
First steps in closing the pool
Your first order of business is to turn off the pump and anything else tied to it before you even consider the filter. Never open a strainer or skimmer basket with the pump running. If there is a multiport valve in the mix, consult the manual for the proper way to shut it down and drain it.
You might follow this kind of routine for a safe start:
- Cut power at the breaker or switch if the equipment manual dictates.
- Be sure the system has come to a complete halt before you open up any fittings or plugs.
- Put on the appropriate PPE when you have to handle worn parts or debris.
Draining the filter and valve
By winter you want the sand filter to be as dry and clean as can be. Hayward and other makers will tell you to backwash as the season requires and keep up with maintenance per their instructions. When it comes time to winterize though, you are after the standing water, not trying to field a repair.
Proceed in this manner:
1. A backwash is in order only if your manual says so prior to shutdown. 2. Put the multiport valve in the position designated for draining in your instructions. 3. Open the port or plug and let the filter run dry. 4. Make sure all the water has left the tank, the valve and the hose sections. 5. Put away the small parts and drain plugs in a spot they won’t be mislaid.
Should you find a seized plug, a brittle fitting or a valve handle that will not budge, leave it be and put in a call to a pro. You do not want to force something and end up with a cracked tank.
Other items to attend to
When you are shutting the pool down for the season, the pump, skimmer and the rest of the plumbing attached to the filter need attention too. Trapped water will expand when it freezes and ruin the equipment.
Once the filter is done with, look over the following:
- The pump housing and its strainer basket
- Accessible lines and the skimmer baskets
- Unions, hoses and any exposed fittings
- Heaters or other accessories on the circulation loop
Do not be tempted to loosen plumbing while the system is live or reach into operating suction. On a complicated setup it is wise to label things before you disconnect them to make the spring startup less of a chore.
Pitfalls to steer clear of
Some of the costliest errors are the simplest ones. That includes leaving water in the plumbing or filter, or using a generic method instead of what the manual prescribes. Forgetting to kill the pump before you get to work is another. And do not think the pool cover is enough to save a water-filled filter from the freeze; it is not.
If you have to use force on a stuck union or plug, or you are mixing up fittings, you are on the wrong track.
Time to call in an expert?
If you are in any doubt about whether the system is truly empty, or how to position the valve and drain it, a pool professional can help. The same goes for any signs of leaks, cracks, electrical issues or water on the equipment pad. Some prefer to have a pro handle the entire closing, from the skimmer to the pump.
In the end, the safest course is to stick to the manual, see that the filter is fully drained and shielded from the weather, and if a part feels unsafe or is not cooperating, just stop.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)