The price of Florida's unregulated and ill-planned growth: 2.6 million septic tanks

[Chainfire]

39. A check valve has to be in a forced system, it does not work in a gravity septic system.

There is a device, that is a check valve of sorts, that is sometimes installed on a house that is connected to a public sewer, it is called a "backwater valve." It is absolutely unnecessary on a septic tank system because, in a gravity home plumbing system, the septic tank can not be above the "flood lever rim" of any fixture. (see reference below) A backwater valve is a service plumber's dream, because he will be there, on a regular basis, cleaning the thing out, to repair stoppages, for big bucks.

Water, even water ponded during a hurricane does not flow uphill. It can be pumped uphill, it can be siphoned uphill (as long as it ends up lower than it started, it can be blown up hill, or it could be carried uphill in a bucket, but it does not flow uphill, not three feet, and not 3 inches and not 3/10s of an inch. You can see the principle working in a "water level."

In your basement, the floor level would almost certainly be below the water in your septic tank, and yes, the tank will flow, by gravity into your basement because it is down hill! Thus the check valve on the pump system. The check valve is not the impediment to flow, in a pumped system, that it would be in a gravity system, because is has the force of the pump to push debris through the valve.

Here is the plumbing code referral: 715.1 Sewage backflow.

Where the flood level rims of plumbing fixtures are below the elevation of the manhole cover of the next upstream manhole in the public sewer, such fixtures shall be protected by a backwater valve installed in the building drain, branch of the building drain or horizontal branch serving such fixtures.


Trust an old plumber, you don't want a check valve on your septic tank system.