The Santa Anas blow through overnight, and by morning there’s a sycamore leaf bigger than your hand parked on the steps, a dozen more sinking toward the main drain, and a skimmer lid that won’t sit flat because the basket underneath is packed solid. This is a normal fall week for a lot of yards around the lake, and it’s a big part of pool service in Westlake Village once the wind starts.

Leaves in the pool look like a cosmetic problem. They aren’t. They change the water chemistry, they can leave marks on the plaster, and the ones that make it into the plumbing go after the pump. Here’s how each of those happens, and what to do about it.

Why fall is leaf season here

A UCLA atmospheric sciences page on the Santa Ana winds says they are “most common during the cool season stretching from October through March.” That’s the same stretch when deciduous trees are dropping, so the wind and the leaves show up together.

The worst offender in a lot of Conejo Valley yards is the California sycamore. Oregon State University’s landscape plant database lists its leaves at 15 to 20 cm long, which is roughly 6 to 8 inches. One of those can cover a skimmer opening by itself. Oak leaves are smaller and stiffer, and they like to collect in the corners and on the steps.

What leaves in the pool do to your chlorine

The CDC lists the things that reduce chlorine in a pool, and dirt is on the list along with sunlight. A pile of wet leaves is a lot of dirt. Everything organic that lands in the water gets attacked by the chlorine, and the chlorine that’s busy with leaves isn’t available for anything else.

The CDC recommends at least 1 ppm of free chlorine in pools, or at least 2 ppm if the pool uses cyanuric acid. A pool that held fine all summer can drop under that in a windy week, especially if the leaves sit on the bottom for days.

Tannins and the leaf-shaped stain

Leaves carry tannins, the same compounds that make tea brown. Orenda, a pool chemical maker, explains that tannins are released as organic material decays, and that the stains are sometimes “the exact shape of leaves.” Its write-up notes that tannins can also tint the water a brownish-green.

The fix Orenda describes is unglamorous: get the leaves and the basket debris out first, raise the chlorine, and brush the stained areas for about a week. Most organic stains fade that way. A stain that ignores chlorine and brushing may not be organic at all, and that’s when people start asking what an acid wash actually does. Try the boring fix first.

Phosphates: leaves feed algae

South Dakota State University Extension, citing a USGS study, calls fall leaf litter “a primary source of nutrients in stormwater, particularly phosphorus,” and points to how easily leaves leach once they’re wet. A pool full of soaking leaves is the same situation in a smaller bowl.

Phosphorus doesn’t turn a pool green by itself, but it gives algae something to work with when the chlorine dips. That’s the combination fall sets up: more food, less sanitizer. If you’re already past cloudy and into green, that’s a full algae removal job, and leaves are only part of the story.

The skimmer and pump baskets are where it gets expensive

Leaves that float get pulled into the skimmer. The skimmer basket catches the big ones, and anything that slips past ends up in the pump’s strainer basket. When either one packs solid, the pump can’t get water.

Hayward’s manual lists a “strainer basket or skimmer basket loaded with debris” as a cause of trouble, and its fix is to “clean the basket, and refill the strainer housing with water.” It also says to “clean strainer basket regularly. Do NOT strike basket.” Banging a basket on the deck to empty it is how you end up buying a new one.

Why a clogged basket can ruin a pump

Hayward’s manual says to “NEVER OPERATE THE PUMP WITHOUT WATER,” and that “running pump dry may damage seals, causing leakage, flooding, and voids warranty.” A pump pulling against a skimmer full of sycamore leaves is getting close to dry.

You can usually hear it. The pump gets louder and rougher, the strainer lid shows air instead of water, and the returns go weak. A shaft seal that cooked once tends to start dripping later, and a dripping seal eventually becomes a pump repair with bearings in it.

If the pump lost prime, Hayward says priming can take up to 10 minutes, and to stop the motor and find the cause if it doesn’t prime in that time. A clean basket and a full strainer housing fix most of these. If it still won’t catch, Hayward notes that “any self-priming pump will not prime if there are suction air leaks.”

What gets past the baskets

Leaves break into fragments, and the fragments go to the filter. A fall full of leaf grit shows up as rising filter pressure and shorter runs between cleanings. If the pressure climbs back fast right after a cleaning, read up on the signs a pool filter is going bad before blaming the trees for everything.

Pool cleaners have their own limits. A suction cleaner sends what it picks up to the skimmer or the pump basket, so on a heavy leaf day it can clog things faster. Pressure cleaners with their own debris bag need that bag emptied, or they just drive around full.

A week of leaves, problem by problem

Asked at the pad, every week

Is it bad to leave leaves in pool water overnight? One night won’t ruin anything. A week of leaves on the floor will cost you chlorine and possibly a stain. Pull the floaters before bed if you can; they’re the easy ones.

Should I run the pump longer when leaves are falling? Only if the baskets can keep up. A longer run with a packed skimmer is just more time pulling against a clog. Empty first, then decide.

Does a leaf net over the pool help? Yes, if it’s tight enough that leaves don’t pile up in the middle and dump in when you pull it off. Anything that keeps leaves off the water beats chasing them on the floor.

Can I turn the pump off during a Santa Ana to stop the skimmer clogging? You can, but the leaves still land and sink, and the water still loses chlorine. You’re trading a clogged basket for a dirty floor.

Keep the baskets empty until the trees are bare

During leaf season, the job is basically netting, baskets and chlorine, more often than you’d do it in July. If you’d rather not, that’s what weekly pool maintenance covers, and the tech emails a report with photos and water readings after every visit, so you can see the baskets and the chemistry without walking outside in the wind.

If the pump already sounds rough or the floor is stained, send us a note with a photo and we’ll take a look. We service Pentair, Jandy, Zodiac, Hayward and Sta-Rite equipment, or call (805) 586-2055.