Do catch basins need cleaning?

Yes, catch basins need cleaning. Their sump is built to trap leaves, mulch and roof grit so the pipe stays clear, and that debris builds up until the basin overflows or the outlet clogs. Clean yard basins after fall leaf drop and after the first big spring storm. This guide from Rein Irving Drainage Company covers when and how.

Why basins fill up

A catch basin is a grated box set at a low point. Water drops through the grate into the box, slows down, and leaves through a pipe set a few inches above the bottom. That gap below the pipe is the sump. Heavier material settles there instead of washing into the line.

Over time the sump fills with:

• Leaves and seeds, especially from live oaks, pecans and cedar elms near the grate.
• Mulch and soil washed out of beds in heavy rain.
• Shingle grit, where downspouts feed the basin.
• Grass clippings blown in by mowers.

The sump is the reason a basin suits surface puddles on clay better than a buried drain does; see French drain versus catch basin.

When the sump is full, debris starts entering the pipe. A pipe with a blockage backs water up into the basin, and then the basin overflows onto the lawn it was meant to drain.

When to clean

Basins under trees, below mulched beds or fed by downspouts need more frequent attention than one in open lawn.

How to clean a yard catch basin

1. Lift the grate. Most yard grates pull straight up or twist out. Clear debris from its slots.
2. Scoop out the sump. A gloved hand, small trowel or shop vacuum works. Remove everything down to the bottom of the box.
3. Check the outlet opening in the side of the box. Pull out any leaves or roots stuck in it.
4. Run a hose into the basin at a steady flow for a few minutes.
5. Walk to the outlet, whether a pop-up emitter, swale or curb core, and confirm water comes out at a steady rate.
6. Clear the outlet too. A pop-up emitter buried under grass or mulch will not open; a curb core packed with leaves backs up the whole line.
7. Replace the grate slightly below the surrounding lawn so water reaches it first and grass does not grow over it.

If water does not reach the outlet, the blockage is in the pipe. A garden hose with a jet nozzle can push out light debris. A line that stays blocked needs a drain snake, jetting or a camera to find the problem; drainage repair covers that.

Signs a basin needs attention

• Water standing in the basin a day or more after rain. The outlet or the pipe downstream is blocked, or the line has lost its fall.
• Water ponding around the grate while the basin is not full. The grate is clogged, or the grass and soil around it have grown higher than the grate.
• Water bubbling up from the grate in a storm. The pipe downstream cannot carry the flow, often because of a partial blockage.
• No water at the outlet during rain. The line may be crushed, disconnected or full of roots.
• A sinking spot near the basin or along the line. Soil may be washing into a broken joint.
• Bad smell. Standing water and rotting leaves in the sump.

If water is standing on the lawn rather than in the basin, start with the standing water page.

Mosquitoes

A basin that drains properly holds very little water and dries out between storms. One that stays full because of a blocked or flat outlet can hold water for a week or more, long enough for mosquitoes to breed. Cleaning the sump and clearing the outlet solves the drainage problem and the mosquito problem together. A basin that holds water even when clean usually has a pipe with no fall, which is a repair, not a cleaning job. On a lot with no lower outlet at all, the line may need a sump pump.

Seasonal checklist

Making cleaning easier next time

A deeper sump, a lift-out basket insert and a cleanout at each turn all make maintenance easier. When a basin is part of a larger yard drainage system, plan those details in at the start.

Next step

If a basin still holds water after a good cleaning, the problem is downstream. Send a photo of the grate and outlet, or see the catch basin cost guide and the cost tool if a basin needs replacing.

Questions people ask

How long does it take to clean a yard catch basin?

For a typical small yard basin, a few minutes: lift the grate, scoop out the debris, and run a hose to check the outlet. Flushing or clearing a blocked pipe downstream takes longer.

Can I put a leaf guard or filter inside the catch basin?

Some basins accept an insert basket that lifts out for emptying, which makes cleaning faster. A fine filter fabric over the grate is a poor idea because it clogs quickly and stops water from entering at all.

Should catch basins be cleaned before a storm is forecast?

If it is easy to do, yes. A quick check that the grate is clear of leaves and mulch before a heavy storm costs nothing and keeps the basin from being bypassed when it matters most.