Thick Scum Layer in Septic - Why??

Old 02-14-23, 09:28 AM
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Thick Scum Layer in Septic - Why??

Every time I get my septic pumped the guy complains of a lot of hard grease in the scum layer of our tank however, we are extremely careful not to put any type of fats, oils, or grease (FOG) down the drain. In fact, we hardly ever fry anything and when we do we always wipe the dish clean with a paper towel before washing.

I'm getting the tank pumped every 18 mos now and it still builds up.

I've watched them during pumping and it is a thick greyish layer on top that is hard to punch through but I have no clue where this is coming from. Could detergents or soaps cause that much build up?

Has anyone else encountered this and if so, how did you deal with it?
Old 02-14-23, 11:31 AM
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Soaps also contribute to that layer so it may not be oils. I see that every time we have our tank pumped, it's never been identified as an issue!
Old 02-14-23, 11:47 AM
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Have you been present to observe your tank being pumped?
How much sediment is in the bottom of the tank?

A layer of soft scum is totally normal. It's generally sorta thin, softer and may have some bubbles in it. If your layer is thick and hard that could indicate fats & oils. Even if you don't pour grease down the drain soaps and lotions are also considered oil/grease. A hard layer can also form if the house is used seasonally with the off season when it's not being used when the hard crust can form.

Pumping every 18 months, wile advised, is more frequent than average. Spend some time online looking at pictures and videos (exciting watching!) so you know what a healthy and abused tank look like. This can help you determine if you are being taken by your septic company. Pumping more frequently doesn't hurt your septic system but it gets expensive and disruptive if you have to dig up the yard each time. Some companies will tell people a story so they can get more work. So, stay informed for your protection.

The next time your septic is pumped ask to see if your tank has a filter on the outlet. The filter is great for preventing the scum from escaping the tank and are required in most new installations.
Old 02-15-23, 06:48 AM
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Thanks PD,

Yes, I've watched the system get pumped I have an easily accessible riser. The scum layer gets pretty thick (~8-10") and it's pretty hard. The pumper has to poke it with a stick to break through. Don't have a filter on the outlet but that's a good idea.

We're a family of 4 and it seems like out washing machine and dishwasher are always running so I'm going with the soaps and lotions as the culprit. the washer is a HE front loader and the dishwasher is a new LG.

Any recommendations for septic-safe laundry and dishwasher soap?

Thanks for all the help.

Last edited by SpartaGuy; 02-15-23 at 06:49 AM. Reason: spelling
Old 02-15-23, 10:04 AM
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Could be that something strange is growing in your tank.
Old 03-02-23, 06:45 PM
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Laundry and D/W soaps are not good. What about DW and her other sanitizers around house ?

We use bacteria/enzyme packets about 2x a month. More if DW is doing a lot of laundry. We use Walex Bio-Active and Cabin Obsession septic tank treatments. About $5 a month. We pump every 4-5 years and my observations show a pink scum on top. Pumpers say this is a good thing. And you should have a baffle on your outflow to the field.

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