How often should you pump your septic tank?

Why bother

Skip it and it backs up the drains. This is an essentials-tier job. Skip it and you're inviting the expensive kind of problem, or the dangerous kind.

Why it's a range

It comes down to how many of you there are and how big the tank. A full house on a small tank wants it every two years; a couple on a big one can go five. Three to five years is the honest range, and skipping it is the expensive way to find yours.

What the job involves

1. Find the lids before the truck does. The tank's buried, and the access ports (the risers) might be under a foot of dirt and a season of grass. Knowing roughly where they are saves the pumper digging blind and saves you the bill for the digging.
2. Book a licensed pumper. They bring a vacuum truck, open the tank, and suck out the lot: the liquid, the floating scum on top, and the settled sludge at the bottom, until it's empty.
3. Have them look while it's empty. An open tank is the one time anyone can check the baffles and the outlet filter for cracks, leaks, or muck backing up from the drainfield. Ask, because you won't see it again for years.
4. Let them reseal the lids and rebury the access covers, and let them haul the waste off. It goes to an approved disposal site. You can't legally tip it anywhere else, which is rather the point of paying someone.

Do it yourself, or pay someone?

A pro, no argument. This is one of the few jobs that genuinely isn't DIY: it needs a high-capacity vacuum truck, the waste is hazardous (toxic gases and pathogens), and most places require a licensed hauler to dispose of it legally. Budget around $427 on average, most homes land between $291 and $563, and a larger tank runs $700 and up.

What skipping it costs

$3,000 to $20,000 is what a failed drainfield costs to put right, and a full tank-and-drainfield replacement averages around $6,000. Skip pumping and the tank fills with sludge until the solids get pushed out into the drainfield, the bed of soil and pipe that does the actual filtering. Once that's clogged with solids it can't be cleaned, only dug up and replaced. Pumping on schedule, the roughly $427 job, is the whole thing that keeps the solids out of it. Before the drainfield goes you usually get the warning shots: sewage backing up indoors and effluent surfacing in the yard.

Signs it's overdue

• Slow drains all over the house, pipes that gurgle, or sewage backing up into the lowest toilets and drains. The tank's full and has nowhere left to put it.
• A sewage or rotten-egg sulfur smell around the tank, the cleanout, or the drainfield. The tank should be doing its business out of nose-shot.
• Soggy ground, standing water, or a patch of grass over the tank or drainfield that's suspiciously green and lush when it hasn't rained. That's effluent surfacing, which is the yard telling you the system's overflowing.

When to start thinking about it

This usually means booking someone, so the grumbling starts 30 days ahead to leave time to line it up. Mark it done and Grumpty sets the next one, every 36 months, so you can go back to forgetting it exists.

Questions people ask