How to Drain a Pool With a Hose: Siphon Method Step by Step

If you're working out how to drain a pool with a hose, the method is a siphon, and it runs on gravity. The outlet has to sit lower than the pool's water surface and the hose has to be full of water to start, and then it runs until the pool end sucks air. Each hose moves roughly 2 to 6 gallons a minute, so a siphon suits partial drains and small above-ground pools, not emptying a 20,000-gallon in-ground pool.

When a hose siphon makes sense

A siphon suits partial drains: dropping the level a foot or two to dilute high stabilizer or calcium, lowering it for winter, or getting below a fitting for a repair. It also suits above-ground pools up to about 15,000 gallons, where three hoses can empty most of the water in about a day.

A siphon only works when the outlet sits lower than the water, so a pool at the lowest point of the lot needs a pump. So does a full in-ground drain, and because groundwater can push up an empty shell, that's one to plan with a pool professional. The complete draining guide covers those methods, and when you should drain a pool explains why most problems don't need an empty pool.

What you need

• One to three garden hoses. A 3/4-inch hose moves noticeably more than a 5/8-inch one, and 50 feet drains faster than 100.
• A weight to hold the pool end at the depth you want.
• A spigot or a wet-dry vacuum to prime the hose.
• A test kit, because many cities want chlorine near zero and pH near neutral before pool water is discharged, in some places even to the sewer.
• A discharge point lower than the pool's surface that is allowed to take the water.

Starting the siphon: three ways that work

Never start a siphon by mouth on pool water.

1. Submerge and cap. Feed the whole hose into the pool and push it under until no more bubbles come out of either end. Cap one end tightly with your palm, keep the other end under water, and carry the capped end over the wall and down to the discharge point. Release it below the level of the pool surface and the water starts to run. This is easiest with a 50-foot hose.
2. Spigot push. Screw the outlet end onto a spigot, weight the pool end in the pool, and run the tap until water pours into the pool with no air in the stream. Shut the tap, unscrew the hose with your thumb over the end (or close a shut-off valve on the hose first), then lower it to the discharge point and open it. Use a spigot with a hose-bib vacuum breaker, since a hose running into pool water is a backflow risk for the house supply.
3. Wet-dry vacuum. Lay the hose with the pool end submerged and weighted, hold the vacuum hose tight over the outlet end, and run the vac until water arrives. Pull the vac away and drop the end. This works on any length.

If nothing flows, air got in, so start again.

How fast a hose drains (per hose, by drop)

Flow depends on the vertical drop from the pool's surface to the outlet and on friction in the hose. The figures below are our physics-based estimates for a 50-foot hose in decent condition. Kinks and worn fittings cut them, so time a bucket at the outlet.

A 100-foot hose runs roughly 30 percent slower, and flow drops as the level falls and the drop shrinks.

As a worked example, a 24 ft round holds about 280 gallons per inch, so lowering it 12 inches removes about 3,400 gallons. One 5/8-inch hose with its outlet 3 feet below the starting level takes about a day, since the drop shrinks to 2 feet as the water falls, and three hoses take about 9 hours. Emptying the pool (about 13,600 gallons) with three 3/4-inch hoses running to ground 2 feet below the pool floor takes about 16 hours. How long draining takes compares these with pumps.

Two or three hoses at once

Each hose is its own siphon, so three hoses move three times the water. Start them one at a time and weight the pool ends at the same depth a couple of feet apart, so one doesn't pull air when another disturbs the water. Going over the top rail is fine, as long as the outlet sits lower than the water surface.

Where the water should go

Discharge rules are local, so check your city's stormwater or wastewater page first. Many cities want pool water in the sanitary sewer through the cleanout at the house, sometimes with a flow limit or advance notice. Others allow dechlorinated pool water into the street or storm drain, and some ban that outright and fine for it. Salt pool water is often barred from storm drains and lawns. Use the lawn only where it's allowed, and keep the water off the neighbor's property.

On an above-ground pool, keep the outlet well away from the base. Thousands of gallons soaking the ground under one side of the wall can leave a level pool out of level.

Stopping before you hit the liner floor

A siphon stops on its own when the pool end sucks air, so for a partial drain, weight the hose end at the target level and the flow stops there.

Don't drain a vinyl-liner pool to the floor unless the liner is coming out. Liner makers warn that vinyl left dry in the sun shrinks, and some above-ground manuals say to keep at least 12 inches of water in when the liner stays. An in-ground vinyl pool shouldn't be fully drained without a pool professional. For a liner change, the siphon gets you to the last inch or two and a wet-dry vacuum finishes.

The refill is the easy half: a 24 ft round is 23 to 45 hours by hose, or 2 to 3 tanker loads of 6,000 to 8,000 gallons, usually done the same day. The above-ground pool fill page covers a delivered fill, and pool refill after drain covers timing the water around your contractor.

Frequently asked questions

Do I have to suck on the hose to start a pool siphon?

No. Submerge the hose and cap the end, push water through it from a spigot, or pull it through with a wet-dry vacuum.

Why does my siphon keep stopping?

Air is getting in, or the drop has run out. The pool end may have lifted, a kink may be choking the flow, a coupling may leak, or the water may have fallen to the outlet's height. Weight the pool end deeper, straighten the hose and move the outlet lower.

Can I siphon an in-ground pool completely?

Usually not, because on a level lot the deep end sits below any outlet you can reach. A full in-ground drain also needs a pump, a check on the groundwater and, on many concrete pools, the hydrostatic relief valve, so involve a pool professional.

How long does it take to drain an 18 ft round pool with a hose?

An 18 ft round with 4 feet of water holds about 7,600 gallons. With the hose ends on ground 2 feet below the pool floor, one 5/8-inch hose takes roughly 45 hours, three take about 15, and three 3/4-inch hoses about 9.

We don't drain pools, but we can bring the water once yours is empty, and many above-ground pools take one or two loads. Send us the ZIP and the size, and a person will reply with one delivered price. Start my quote.