How to Drain a Pool in Los Angeles Without Damaging It

Most pages on this subject are a hose-and-pump tutorial, and the mechanics really are that simple. What they skip is that plaster is meant to sit under water, that groundwater can lift an empty shell, and that in Los Angeles the water has a legal place to go. This is the order to think about it in.

First, check you need to drain at all

People drain a pool to fix a water problem far more often than a pool needs it. Most of these do not call for it:

• Green water. It is a chemistry job. The green pool page covers it without losing a gallon.
• Cloudy water or a failed test. Fix the readings in order, as the pool chemistry page lays out.
• Too much stabilizer. A partial drain is the only fix, but done in stages: see the stabilizer page.
• Stains on the plaster. Some answer to brushing or chemistry, and some need the pool empty. Find out which before you pull the plug.

A full drain is for work that cannot be done underwater: an acid wash, resurfacing, a structural or plumbing repair, or a pool that is coming out. If nothing on that list applies, leave the water in.

Then check the ground

A full pool holds itself down. An empty one is a big shell buried in soil, and where the groundwater is high it can push the shell up out of the ground or crack it. That risk is highest after rain, so wait for dry weather, and ask before you drain if the yard is on a hillside or the soil has been wet. Our after-rain page explains why the water table is the thing to watch.

Heat matters too. Bare plaster left to dry in the sun can craze, so a drained pool should not sit for days. Pick a cool, dry spell, and plan to refill the same day the work inside is done.

Where the water is allowed to go

Pool water is chlorinated, and storm drains run to the ocean without treatment, so the street and the gutter are out. The usual answer is the sanitary sewer clean-out on your own property, the same route filter backwash takes. LA Sanitation's guidance for residential pools points there, asks for the water to be dechlorinated first, and asks you to avoid draining in wet weather. Other cities in the county have their own rules, so check with yours before the first gallon.

To dechlorinate, stop adding chlorine days ahead, including tablets in the feeder, and test until the reading is at zero. A neutralizer from a pool store speeds it up. If you cannot find the clean-out or are unsure it is the sewer line, stop there: sending water into the wrong pipe is the one mistake that cannot be undone.

How to do it

1. Dechlorinate and test. Chlorine at zero, pH in a normal range.
2. Switch off the equipment. Pump, heater, salt cell and any auto-fill, so nothing runs dry or tops the pool back up.
3. Set the submersible pump on the floor near the shallow end, hose attached and run to the clean-out. Use a ground-fault outlet and keep the cord out of the water.
4. Cover the clean-out with a screen, rest the hose on it, and start the pump.
5. Stay close. Hoses slip off, and the pump can lose its grip as the water gets shallow.
6. Never use the main pump to drain. It is built to move water that comes to it, and running it dry burns the seal.

How long it takes

Our price list puts most Los Angeles back-yard pools at 15,000 to 25,000 gallons. A small utility pump moves roughly 30 to 50 gallons a minute, which is our estimate and not a rating for any one model, so a 20,000-gallon pool takes around eight hours. A garden hose on its own is far slower, closer to days than hours. The last inch or two is slower again and ends with a mop or a wet vac.

Refill straight away

Start the hose as soon as the shell is done. Stopping mid-fill can leave a ring on the plaster, and a hose fill takes the best part of a day, as our acid wash page notes. Watch the level so it stops at the middle of the tile line. The fresh water arrives with no chlorine and no stabilizer, so test it once it is full and bring it back up in order.

What it costs

Doing it yourself costs a pump rental, a day of watching, and the water to refill. If the reason for draining is plaster that needs washing, we do the whole job: a drain and clean, from $749 for the pool, as the acid wash page shows, with the pool refilling inside the same day.

Not sure the pool needs draining? Send us the symptoms and your last readings and we will tell you before anyone touches a valve, or call (818) 740-6099.