Septic Pumping and Repairs

Fauquier, Fairfax, Stafford, Culpeper, and Prince William Counties.

Septic tank fantasy No. 1: we need to pump out the septic tank whenever the septic tank gets full

Wrong.

A septic tank in normal use is always full, right up to the bottom of the outlet pipe (near the top of the tank). After pumping it out completely, an empty septic tank fills up again under normal usage in just a few days, after which it is again discharging liquid effluent to the absorption field, soakaway bed or leach field - names vary by country.

In a normally-working conventional septic tank we find wastewater, or "blackwater": a combination of watery sewage effluent, a floating scum layer at the tank top (in Austraila the "scum blanket", and settled sludge in the bottom of the tank.

If as in the sketch above we could see a cross section of the septic tank contents (if we wanted to) we would know when pumping the septic tank is actually necessary based on its sludge and scum layers - that is, based on data instead of either theory or wild arm-waving.

A septic pump-out is needed when the thickness of the floating scum layer and settled sludge layer occupy so much of the tank volume that the free liquid area is "too small" - the "net free area" has become so small that

the EFFLUENT RETENTION TIME, the time that wastewater has in the tank to allow for solids and floating scum to separate from effluent being discharged to the drainfield (soakaway in the U.K.) is too short. This gives new meaning to time is short, right?

Short septic tank effluent retention time means we're pushing solids into the drainfield, clogging it up & shortening its remaining life.

Two valid septic tank cleaning approaches involve either using