7 signs your septic tank is full. And what to do about it.

Every septic tank fills up. Solids settle to the bottom as sludge, grease and light material float to the top as scum, and the clearer water in the middle flows out to the drainfield. Pumping removes the sludge and scum before they build up far enough to escape into the drainfield, where they clog the soil. That damage is slow, expensive and often permanent, so it pays to know the warning signs.

The 7 signs

1. Slow drains throughout the house

One slow sink is usually a local clog. Several fixtures draining slowly at once, especially on the lowest floor, points to the tank or the line leading to it.

2. Gurgling sounds

Gurgling in drains or toilets after you run water means air is being pushed back through the plumbing because water cannot leave the house freely.

3. Sewage odor inside or outside

A rotten-egg smell near the tank, the drainfield or inside the house is a sign that gases are escaping where they should not. Check our guide to septic smells for other causes.

4. Water backing up into tubs or floor drains

Water rising in a basement shower, tub or floor drain when you do laundry or flush is a classic sign the tank or line is full. One customer called us when water was backing up into a downstairs bathtub.

5. Soggy ground or standing water over the tank or drainfield

When the tank is overfull, effluent can surface around the lids or over the drainfield. In our wet winters it is easy to blame the rain, but a spot that stays soggy after the rest of the yard dries is a warning.

6. Unusually green grass over the drainfield

A stripe or patch of lush, bright green grass over the drainfield in dry weather can mean it is getting more liquid, and more nutrients, than it should.

7. It has been more than three to five years

If you cannot remember the last pumping, or you just bought the home and the records do not show one, assume it is due. Most households need pumping every three to five years. See how often to pump a septic tank.

What to do if you see these signs

1. Cut back on water right away: spread out laundry, skip the dishwasher, take shorter showers.
2. Do not use chemicals or additives to “fix” it. They do not empty the tank and can push solids into the drainfield.
3. Find your records. Your last pumping report is in your county’s online records in both King County and Snohomish County, along with your as-built (the drawing showing where the tank is). Our guides cover King County as-builts and Snohomish County as-builts.
4. Book a pumping. We pump the tank, measure what was in it, check the baffles and filter, and file the pumping report with the county for you. Routine pumping starts at $590 plus the county report fee and tax (see pricing).

When it is more than a full tank

Sometimes a tank is pumped and the problems come back quickly. That usually means something else is going on: a blocked line between the house and tank, a failed pump on a pressure system, a clogged filter, roots, or a drainfield that is saturated or failing. When we pump, we look for these, and we will tell you if the tank was not the real problem. See signs of drainfield failure and our sewer line jetting service.

Staying ahead of it

The easiest way to never see these signs is to pump on a schedule and have the system checked regularly. Our Septic Maintenance Plan ($20 a month, cancel any time) includes a free annual filter cleaning and system check, reminders when pumping is due, and 10% off every pumping.

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