Liquid Chlorine for Your Pool in Los Angeles: Dose, Timing, Storage

Liquid chlorine is sodium hypochlorite in water, the same chemical as household bleach but stronger: pool-grade jugs run 10–12.5%. It works the moment it hits the water, there is nothing to dissolve, and it leaves nothing behind except a little salt.

How it differs from the other chlorine products

Every kind of chlorine does the same job. What differs is what comes along with it, and in Los Angeles, where tap water already brings plenty of minerals, that decides which one stays in the shed.

• Liquid chlorine (10–12.5%): no stabilizer, no calcium. It raises pH a little.
• Calcium hypochlorite (granular shock): strong and cheap, but it adds calcium every time, and the calcium ends up as scale on the tile.
• Trichlor tablets: slow and convenient, but about half of each tablet is stabilizer that never leaves the water. They also lower pH.
• Dichlor granules: dissolve fast, and also carry stabilizer.

The stabilizer side of that list has its own page, the cyanuric acid guide. If tablets have pushed yours too high, liquid chlorine is the usual way to stop feeding it.

How much to pour

The dose is arithmetic, and the label strength is the input. One gallon of 10% liquid chlorine raises free chlorine by about 10 ppm in 10,000 gallons of water. A 12.5% jug raises it by about 12.5 ppm. So to add 1 ppm per 10,000 gallons you need roughly 13 fluid ounces of 10% product, or about 10 ounces of 12.5%.

Take a 15,000-gallon pool with a 12.5% jug and a goal of raising chlorine by 3 ppm: 3 × 10 ounces × 1.5 comes to about 45 ounces, a little over a third of a gallon. Where the reading should end up is on the pool chemistry page: 1–3 ppm for most pools. The doses for a green pool are higher and depend on the colour of the water, and they sit on the green pool page.

Not sure of your volume? Length × width × average depth × 7.5 gives gallons, close enough for dosing. A jug that has sat for months is weaker than its label, so test after the dose and add more only if the reading says so.

How to add it

1. Wait for dusk. Sun burns chlorine off fast, and evening gives it the whole night to work.
2. Run the pump and put on goggles and gloves.
3. Measure into a clean cup, then pour slowly into the water in front of a return jet, walking the edge if the pool is large. Never pour it into the skimmer.
4. Brush the walls if the pool has algae, so the chlorine reaches the surface.
5. Test after an hour. Swim only when free chlorine is back in the 1–3 ppm range.

Why it vanishes in the sun

Liquid chlorine carries no stabilizer, so strong sunlight breaks it down quickly. A pool with no stabilizer at all can lose most of a dose within a couple of hours of afternoon sun. That is why the same pool needs a little stabilizer in the water, within the range on the stabilizer page, and why liquid chlorine goes in after sunset.

It also raises pH slightly with each dose. If you pour often, test pH once a week and see the alkalinity and pH guide when it creeps up.

Buying and storing it

Buy plain sodium hypochlorite, 10–12.5%, from a pool store or a hardware store. Skip anything scented, thickened or sold as splashless bleach: the additives are made for laundry, not for water you swim in. Household bleach is weaker, and you would pour a lot more of it.

The product loses strength with age, heat and light. A garage in a Valley August is the worst place for it. Buy what you will use in a few weeks, keep it upright in a cool shaded corner, and use the oldest jug first.

Safety

Never mix liquid chlorine with acid, with another chlorine product or with a cleaner: the mixture gives off chlorine gas. Keep jugs where children and pets cannot reach them, add chlorine to water and not the other way round, and rinse splashes off skin right away.

When liquid chlorine is the wrong tool

It keeps a clear pool clear. It does not turn a green one back by itself: brush, balance and shock in rounds, which the green pool page lays out. Yellow dust on the walls needs a different approach, see the mustard algae page, and a salt pool makes its own chlorine, so the saltwater maintenance page covers when a jug is needed at all.

What it costs

Doing it yourself, you pay the store's price for each jug, and that price is the store's, not ours. How many jugs you need depends on pool volume, sun and how much stabilizer is in the water.

A weekly visit begins with a chlorine reading, and any dose it calls for comes off our truck. Standard chemicals sit inside the monthly price from $159, as the price list shows. What else the visit includes is on the weekly maintenance page.

Want someone else to carry the jugs? Send us your readings and a photo of the water, or call (818) 740-6099.