I dug a 8ft X 6ft pit to drain my sinks, bathtubs and washing machine water into. The ground had right much clay but was able to get past that and into sand. I put 4 ft of rock in the pit, ran a 4" pipe from the house to the pit resting in the rock in the pit. I don't have a problem with the bath or sink water, but the washing machine water comes back above the surface of the ground. I did not put any kind of barrel in the pit. Can anyone help me with this and tell me what I have done wrong? Thanks in advance on any suggestions to get this right

  • you still need soap filter, otherwise it will clog your drain.
    – Traveler
    Jun 25, 2022 at 20:07
  • "8ft X 6ft pit" - "4 ft of rock in the pit" - 8' long, 6' wide, and 4' deep, all filled with stone? So it's a french drain (filled with rocks covered with dirt? And you're discharging soap into it....) and you expect it to act like a septic tank (with actual capacity - opposed to a storm drain which is 'w/e' if it comes to the surface, as long as it isn't next to the house, seeping in, and all grade pitches away). How to build a septic tank?
    – Mazura
    Jun 25, 2022 at 22:41
  • 4
    "What is an illicit discharge? The United States Environmental Protection Agency defines an illicit discharge as, “any discharge into a storm drain system that is not composed entirely of stormwater.” This means that anything other than simply the water that falls from the sky is an illicit discharge. There are many hazardous household products, yardcare products, fertilizers, dog waste, car soaps and automotive fluids that turn what should only be stormwater into an illicit discharge that pollutes and degrades local water quality." cwsec-sc.org/what-is-an-illicit-discharge
    – Mazura
    Jun 25, 2022 at 22:57
  • 1
    Presumably what you did wrong was fail to meet code for either of those types of systems (not that I know what that is, I'm municipal). And if you did met your code, you did the absolute minimum and should follow some code written in a country that has an EPA.
    – Mazura
    Jun 25, 2022 at 23:09
  • en.wikipedia.org/wiki/Dry_well
    – Jasen
    Jun 26, 2022 at 5:12

2 Answers 2


Washing machine puts out water faster?

I take

but the washing machine water comes back above the surface of the ground

to mean you see water atop your pit. If all three wastewater sources (sink, shower, washing machine) share the same drain line maybe it is because the washing machine drains a lot of water fast? Or perhaps the sink and shower drain pipe systems are larger before they enter the common pipe and so act as a reservoir to limit the rate at which these wastewater sources enter the common drain. The washing machine just goes right to the common pipe.

Your barrel idea is a good one. Have a barrel in the pit with an opening in the bottom to allow it to drain into the sand. Have the common wastewater pipe enter the barrel. The barrel can hold a lot of water and then allow it to drain in an orderly manner. Also if you put a screen or even a rag in the drain at the bottom of the barrel it will give you easy access and let you clean out scum, particulates and hair that will eventually clog up your sand and make your pit useless.

Last and an idea that I keep having - block the barrel drain and then use the graywater to irrigate thirsty trees in the summer!

You should put a cover over your barrel or animals might fall in at night.


Soap, Soap, Soap

Will clog your drain in no time.

You have the right size pit, of 225 cubic feet = 1,500 Gallons.

The washing machine outputs up to 40 Gallons.

So why is your pit not draining?

Look at he bottom and find out there is a soap layer covering the bottom. Over time it will simply fill up and spill over.

Since you are using slow drain in you pit, the soap will settle down and block it.

You need a soap filter before the pit.

You can buy one or build it your self.

There are many DIY soap filter, where using mosquito net is simplest.

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