How to Lower a Pool's Water Level

What is the best way to lower a pool's water level?

The right tool depends on how much water you need out and how fast. For a controlled drop of a few inches, a submersible utility pump or an automatic cover pump on a discharge hose gives the most control: set it in, run the hose to where the water can legally go, and pull it out when the level is right. A cover pump shuts off on its own, which is handy if you cannot babysit it.

If you own a sand or DE filter with a multiport valve, the fastest route is the pump's Waste setting, which sends water straight out the backwash line while the pump does the work. That method has one catch worth its own section below.

With no pump at all, a garden-hose siphon works for a slow drop. Fill the hose completely with water, cap both ends, put one end in the pool and drop the other end downhill somewhere lower than the pool surface, and gravity pulls water out until you break the siphon. It is slow but costs nothing. A cartridge filter has no waste line, so on those pools you use a pump or a siphon.

What level should the water sit at?

A pool runs best with the water at the middle of the skimmer opening, roughly one-third to one-half of the way up the skimmer mouth. That is your target after rain: bring it back down to mid-skimmer, not lower.

The level matters because the skimmer only works in a narrow band. If the water climbs above the top of the skimmer opening, floating debris stops getting pulled across the weir and the surface goes still and dirty. If it drops below the bottom of the mouth, the pump starts pulling air instead of water. The mechanics are in how a pool skimmer works.

Winter closing is the exception to the mid-skimmer rule. How far you drop depends on the cover and the climate: a solid cover usually sits just below the skimmer, a mesh safety cover a few inches lower than the returns, and in freeze country you clear and plug the lines no matter what. Some owners skip lowering entirely with a skimmer cover plate. The winterizing guide has the full sequence, and you should not over-drain a vinyl pool to close it.

How do you lower the water fastest with a sand or DE filter?

On a sand or DE filter, the fastest way to drop the level is the multiport valve's Waste (or Drain) setting, which routes water straight out the backwash line instead of back through the filter and into the pool. Turn the pump off, move the valve to Waste, then restart, and the pool level falls as water leaves through the waste hose.

Watch the level the whole time. Because the water is leaving through the skimmer, once it drops to the bottom of the skimmer mouth the pump starts pulling air, loses prime, and can be damaged running dry. Turn the pump off before it gets there, or feed it from a main drain if your pool has one. Never leave a Waste drain running unattended.

A cartridge filter has no Waste position, so this trick does not apply; use a submersible pump or a siphon instead. The valve steps are the same ones in how to backwash a sand filter. Only drain to waste this way when you genuinely need the level down, since it dumps clean, balanced pool water you paid to treat.

What should you do after heavy rain overfills the pool?

After a heavy rain, lower the water back to mid-skimmer, then test and rebalance. Rain does two things at once: it raises the level and it changes the chemistry, and you fix them in that order.

Get the level right first so the skimmer works again. Pump or backwash out enough to return the water to the middle of the skimmer opening. If the water only rose an inch or two and is still within the skimmer mouth, you may not need to remove any at all. A pool does not need draining every time it rains, only when the level climbs above the skimmer or the water threatens the deck, coping, and equipment pad.

Then handle the chemistry. Rain dilutes your chlorine and drops pH and total alkalinity, and it washes in dirt, pollen, and phosphates, which is why pools often turn cloudy a day later. Test the water and bring chlorine back to target with the chlorine calculator. The full recovery playbook is in why a pool is cloudy after rain.

Is it safe to lower the water a lot?

Lowering the level a few inches to a foot is safe on any pool. Draining it far down is a different job, and that is where the risk starts.

On a vinyl-liner pool, dropping the water well below the return lines lets the liner dry out, shrink, and wrinkle, and it can pull loose from the track, so never lower a vinyl pool more than the closing instructions call for. On an inground concrete or fiberglass pool, a full drain risks the empty shell floating up out of the ground on groundwater pressure. Those are full-drain problems covered in how to drain a pool; a routine few-inch drop never reaches them.

Know where the water goes before you start. Chlorinated and especially salt water should usually go to the sanitary sewer through a cleanout, not the storm drain, and salt water kills grass and plants where it runs. Check local rules, since some areas regulate where pool water can be discharged.

Frequently asked questions