Septic Tank Pumping Procedure

Return Septage or Liquid Back to the Septic Tank After Pumping?

A number of readers have asked about the practice of some septic tank cleaning companies of returning some of their pumped-out contents to the septic tank at the end of the job.

The septic pumpers give various explanations for this practice, for example, claiming that some "starter" bacteria is necessary or that a septic tank shouldn't be left "dry".

Bottom line: Watch out: That is not correct, and worse, returning septage to the septic tank risks early failure of the septic drainfield - a costly mistake, as we explain here.

Photo: a septic tank pump inlet assembly from masaportprtpump.com - there is no septic filter used on a typical septic system pumper truck.

Also see RETURNING "WATER" to the SEPTIC TANK AFTER PUMPING, FAQs

Our septic tank pumper reverses the truck pump and fills the tank back up: is that standard practice?

During past septic tank pumpings, the operator would pump out the tank, have me flush a toilet near the tank end of the house pump that out and then reverse the tank truck pump and fill the tank back up with gray water (presumably).

Is it standard practice to refill the tank from the pump truck? On 2020-05-29 by Wolf

Answer by (mod) - Watch out: No, it's a bad idea: septic pumper truck should NOT return septage or effluent containing suspended solids to the septic tank

Wolf

Other readers have reported this same - In my OPINON - questionable practice.

Re-filling a properly-installed septic tank after pumping is unnecessary and unfortunately creates a high risk of pushing small floating solids into the drainfield, drastically shortening its life and leading to a costly repair.

This is particularly concerning because the process of breaking up sludge and scum layers, mixing that with effluent, passing that through the septic vacuum pump and into the pumper truck's tank is absolutely going to cause a very high level of suspended solids in the liquid effluent.

That's the worst sort of material to return to a septic tank and thence to allow out into a drainfield.

ONLY if there is a septic effluent filter at the septic tank outlet tee might you be protected from serious septic field damage or life reduction.

Why would a septic pumper "pump put" your septic tank and then "pump it back again" claiming it's just "gray water"?

The answer is that it costs the pumper a fee to empty their septage at an approved disposal facility. So if the pumper can get paid for "pumping out" your septic tank and then giving back nearly all of what they removed, that's more profitable.

I don't necessarily blame the septic pumper truck driver-operator, as most-often he's simply following the instructions of the owner of the septic pumping company.

I have collected typical septic pumper truck specifications

at PUMPER TRUCKS & VACUUM PUMPS SOURCES / SPECS

No septic pumper trucks include a fine effluent filter to prevent returning suspended solids to the septic tank

Septic pumper trucks usually employ a rotary vane vaccum pump (typical for cleaning home septic system tanks) or a liquid ring pump (preferred if handling corrosive waste liquids).

Rotary vane pumps use spinning "vanes" attached to a central rotor to pull a mixture of solids and liquids out of a septic tank. These pumps are even capable of lifting small stones out of a septic tank!.

There is no small particle filter on the septic pump inlet nor on its outlet.

I have not found any septic pumping trucks that are equipped to pass septic effluent through a fine effluent filter such that returning that liquid to a septic tank would be safe.

There ARE traps and filters on septic pumper trucks intended to protect the vacuum pump from damage.

An example is supplied by Masport Pumps www.masportpump.com/vacuum-truck-components/inlet-filters and is shown here. The purpose of the traps and filters in this case are to protect the vacuum pump.

I will continue research other such pumper truck effluent filtering pump systems & who is using them, but thus far finding nothing of the sort, I'm doubtful.

We would welcome hearing from septic pumping companies and other experts on this topic.

Some septic pumpers return part of the liquid back into the tank: is that recommended?

One septic pumping company would pump the tank dry and rinse with a hose.

A different company pumped out the tank and returned some of the truck content back to the tank and said it puts good bacteria back for the system to get started again.

That’s after I asked if he needed the hose after another company asked for the hose. What is the correct pumping procedure? On 2020-08-14 by Stephen Arlaud

Answer by (mod) - No do not return septage or effluent to the septic tank after pumping: Watch out: that is likely to speed the ruin of the leach field

Pumping out a septic tank followed by pumping the old or effluent fluid back into the tank is basically getting paid for doing nothing useful.

There is absolutely no need to add bacteria to a septic tank. There's plenty of bacteria in wastewater.

See those details at CHEMICALS & TREATMENTS for SEPTICS

And with the sole exception of preventing a steel or plastic septic tank from "floating up out of flooded soils", there is no reason and no benefit to return liquid waste to the septic tank after it has been pumped out. What that's really doing, in my OPINION, is simply increasing the profit for the septic pumping company who then has less septic waste volume to dispose of at a cost to themselves.

Watch out: pumping liquid out of a septic pumper truck and back into the septic tank is likely to return fine floating solids in that wastewater.

Since you're filling the septic tank with fine floating solids in effluent there won't be sufficient settlement time to preven that mix from being pushed out into the septic drainfield as soon as wastewater from the home enters the septic tank - that is the next time a building occupant flushes a toilet or runs water in a sink, shower, tub, etc.

Those solids then readily flow out into the septic drainfield, clogging the soils there and speeding the end of the drainfield's useful life. That speeds the arrival of expensive septic field replacement.

Installing a septic effluent filter at the septic tank outlet tee is an option that can help prevent drainfield destruction from this septic pumping mistake.

See SEPTIC FILTERS for details.