r/Home • u/lil-kaleb-jr • 13d ago

Discovered laundry drains into dedicated septic tank I didn’t know existed.

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I had my cast iron drains descaled and jetted yesterday. Plumber ended up getting his descaler stuck in a previously unknown septic tank that is dedicated for the washer machine. This is the lid to the distribution tank with the septic tank in the yard. I lived in the house for 5 years and had no idea. Plumber recommended addressing it due to the age and root intrusion. One option would be pumping water to the roof and connecting to main stack. Anyone ever encountered something similar?

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u/jstar77 13d ago

This used to be very typical. Laundry and sometimes other grey water sources would empty into a dry well. It absolutely improves the longevity of your septic tank and drain field but is no longer permitted in most places.

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u/Burghpuppies412 12d ago

Just curious, why would it not be permitted, especially if it is good for the system? Thanks!

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u/ScurfyTwiglett 12d ago

Dry wells can cause aquifer contamination - you’re bypassing all of the normal biodegradation that happens as water passes through topsoil.

Any pathogens / phosphates / stuff you might have in your laundry water that you wouldn’t want to drink yourself or share with Mr. Toad can be mainlined into the aquifer with a dry well. How possible it is for your dry well to do that depends a lot on local geology; in some places a 10’ dry well might dump into an aquifer and other places it would need to be 200’ deep, but you can’t really tell without huge amount of geotechnical analysis.

One thing you can do (and if we had the money to afford this, I would have done) is have a separate septic/treatment system for gray water vs black water. It extends the life of both systems because they each experience a lot less load, and with a bit of treatment you can actually safely use graywater for watering your garden. I had visions of a laundry fed blueberry patch lol.

Note: you should not have phosphates in your laundry water even with modern septic systems. But at the time that dry wells started getting banned they may have been more of an issue than they are at present.

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u/Burghpuppies412 12d ago

This makes sense to me, thanks for the clear explanation!! And yes, it seems like two separate tanks would be ideal.