How to Drain a Pool With a Hose

A hose drains a pool only when the outlet is lower

To drain a pool with a hose, fill the hose completely with water, keep one end submerged, and place the outlet below the pool’s water surface. This creates a siphon, which moves water without a pump while the hose stays full and the outlet remains below the falling water level.

A hose can pass over the pool edge and still siphon. The outlet must be lower than your intended stopping level. If the only available outlet is level with or above the pool water, a gravity siphon will not work.

Use this method for a controlled partial drain after confirming your pool’s safe lowering limit. Removing excess water and reducing a measured chemical concentration require different stopping points. Cloudy or green water alone does not mean the pool needs draining.

Check where the water will go and how far to lower it

Before you start, ask your city's wastewater or stormwater agency where the drained water is allowed to go. A downhill driveway, street gutter, or nearby drain is not automatically an acceptable outlet. Requirements can differ across San Diego County. Describe your proposed route and whether the pool uses a salt system. Ask what water tests and flow limits apply.

If draining onto landscaping is permitted, confirm the water meets local requirements before releasing it. Stop adding chlorine and test the chlorine remaining in the water rather than assuming a waiting period makes it suitable. Keep salt-system water off planting beds because dissolved salt remains after chlorine dissipates.

The spot where the water goes must absorb the flow without pooling, erosion, or runoff toward neighboring property. Secure the hose where you can watch the water leave.

Do not empty an inground pool without an assessment. Groundwater pressure can lift an emptied pool. Aboveground pools and liners also have manufacturer limits on lowering water. A slow hose does not remove these risks.

Start the siphon without using your mouth

Gather a garden hose, a way to secure its ends without damaging the pool, and a visible marker for the stopping level. Remove spray nozzles. Use one continuous hose where practical, since connections can admit air.

1. Stop equipment that needs circulation. Let a running heater complete its required cooldown. Turn off the circulation system and prevent scheduled or remote starts during draining. Turn off any automatic refill so it does not replace water as you remove it.
2. Fill the hose underwater. From the pool edge, feed the hose into the water gradually, letting air escape. Keep both openings submerged until the hose is full and bubbles stop.
3. Secure the pool end. Keep the inlet submerged below your planned stopping level, clear of leaves. Do not attach it to a pool suction fitting (the skimmer or wall/floor opening that pulls water to the pump).
4. Seal the outlet temporarily. Cover the opening while it is underwater. Carry that end to the spot your local agency allows without letting water escape or air enter.
5. Uncover the lower outlet. Release it below the pool’s water surface. Water should begin flowing. Secure the outlet and keep the hose out of walkways.
6. Watch the water level and flow. Check that the inlet stays submerged and the spot where the water goes handles the flow.
7. Stop at the mark. Lift the pool end out of the water to admit air and break the siphon. Let water remaining in the hose drain into the same permitted spot.

Never start a siphon by sucking on the hose. If it does not start, check the outlet height, then refill the hose completely before trying again.

Calculate how long your partial drain will take

There is no single draining time for a garden hose. A wider hose generally moves more water; extra length, bends, and a smaller height difference slow the flow. The rate usually drops as the pool surface approaches the outlet height.

First, calculate how much water you plan to remove. For a rectangular pool with straight sides, length in feet × width in feet × 0.623 = gallons per inch of depth. Multiply that result by the number of inches you plan to lower the water. This estimates the water in the shallow layer you remove, so you do not need the pool’s average depth. Curved walls, steps, and irregular shapes require an adjusted estimate.

Next, collect the water leaving the hose in a container of known volume while keeping the outlet at its working height. Divide the collected gallons by the elapsed minutes to find gallons per minute, or gpm. Then divide the planned removal volume by that measured rate to estimate draining time in minutes.

Example: A 15 × 30 ft pool holds about 280 gallons per inch. Lowering it 2 inches removes about 560 gallons. If your hose fills a 2-gallon container in one minute, its measured rate is 2 gpm. At that rate, 560 ÷ 2 = 280 minutes, or about 4 hours 40 minutes.

Treat that estimate as a scheduling aid. Recheck the pool level during draining because the flow can change. Choose a window when you can supervise both ends, rather than leaving the hose running overnight.

If water stops before your mark, check these causes:

• The inlet is exposed: Air has entered and broken the siphon.
• The hose contains air: Refill it and check connections for leaks.
• The hose is kinked or blocked: Straighten it and clear debris from the opening.
• The outlet is too high: Flow stops when there is no useful height difference.

Do not connect the hose to an unidentified equipment valve to increase flow. Our technicians confirm suitable connections after seeing the equipment.

Use a drain adapter only if your portable pool supports it

Some Bestway and other portable pools have a drain valve that accepts a garden-hose adapter. This lets water leave through the valve without filling the hose first to start a siphon. The hose outlet still needs a lower point for gravity drainage.

Check the instructions for your exact model before opening the valve. Confirm the correct adapter, attach and route the hose as directed, and follow the specified cap and valve sequence. Do not force a hose fitting onto an incompatible outlet.

For an inflatable pool without a compatible drain connection, a hose siphon can remove water while its inlet stays submerged. Keep children away during draining and follow the manufacturer’s emptying instructions.

A siphon will leave water behind once its inlet draws air. A drain valve can also leave water below the opening. For a small portable pool designed to be emptied, follow its instructions for removing that remainder. Do not tip or drag a water-filled pool unless the manufacturer permits it. For an inground pool, stop at the assessed limit rather than trying to chase the last water with the hose.

Test San Diego fill water before choosing a replacement amount

If you are draining to reduce calcium hardness, test both the pool and the intended fill water first. Most San Diego County tap water comes from imported supplies, including Colorado River and State Water Project water. It arrives hard and mineral-heavy. Do not calculate a water exchange as though the replacement water contains no calcium.

Replacement water reduces a concentration only when it contains less of that substance than the pool water. For one partial drain followed by a refill, the expected concentration is (pool concentration × fraction retained) + (fill-water concentration × fraction replaced).

For example, if your calcium hardness tests read 600 ppm in the pool and 300 ppm in the fill water, replacing one-quarter of the pool gives about 525 ppm: (600 × 0.75) + (300 × 0.25). Here, ppm means parts per million. That calculation predicts the change; it does not establish a safe draining depth or a target for your pool. If the predicted result would still leave hardness too high, have us assess the exchange plan before removing water.

The same dilution calculation applies to stabilizer or salt when you use their measured concentrations. For a measured partial exchange, drain to the established mark before refilling. Adding fresh water while siphoning sends some replacement water back out and makes dilution harder to calculate. Use sequential draining and refilling only within your pool’s safe lowering limit.

Hotter inland and East County summers increase evaporation compared with the milder coast. Evaporation leaves minerals behind, and topping up adds more minerals with the replacement water. After repeated summer top-ups, retest pool and fill-water hardness before repeating a previous exchange amount. A coastal pool’s draining schedule is not a reliable guide for an inland pool.

Set the restart plan before you begin

Proceed only when your local agency allows the spot where the water goes, your stopping level is marked, and you have time to supervise. During Santa Ana winds, leaves and dust can collect around the inlet quickly. Postpone draining if you cannot keep it clear and watch the outlet.

If you need a large exchange, lack a lower outlet, or do not know your pool’s lowering limit, arrange an assessment first. Our pool draining and restart service can help establish the drainage and equipment plan. Review our San Diego pool service pricing when budgeting for professional help. Have your pool type, approximate dimensions, recent pool and fill-water tests, and proposed spot for the drained water ready.

After the partial drain, refill to the equipment’s required operating water level before restarting circulation. Confirm the pump primes, meaning it fills with water and establishes steady flow, before enabling the heater or salt system. Once the replacement water has mixed thoroughly, retest chemistry before adding corrective chemicals.