So I had to dig out my septic tank to remove the manhole lid that someone buried probably 20-30 years ago. The tank was leaking ground water in at a staggering rate. So now I have installed the 4’ manhole acces to above ground where the lid will sit on that. I picked up 200 lb of Bentonite clay powder that I was gonna backfill the joint from the tank to the manhole. This should help me with ground water.
Upon giving it some thought; I realized that 200 lbs of bentonite can potentially absorb 3000 lbs of water. Am I looking for trouble and a swelling backfill by using this clay? Should I mix it with water during the backfill? Any thoughts or advice from somebody that has used this before?
When I used to mix it for either a mud plug on a sag-d well or a ground water barrier wall, it was mixed with so little water that if the mixture sat still for too long (30 minutes), it would almost turn into a solid. A five gallon pail of it would weigh about 90 lbs. I would mix it in a wheel barrel as close to the hole as possible and dump it in.
There are injectable foams and epoxies that work very well too. As well as Xypex mortars that may work better for you.
I will have the cheesy tar strip they use to seal the sections together then planned to add the clay to the outer joint as the water table is above this currently. Would any of the products you speak of set-up basically under water?
You're just sealing the manhole to the tank?
The butyl tape will take care of that.
Just get the surfaces really clean/dry.
Use a wire wheel on a drill.
__________________
"I like to quote my own quotes" ~ Dewey Cox
You're just sealing the manhole to the tank?
The butyl tape will take care of that.
Just get the surfaces really clean/dry.
Use a wire wheel on a drill.
I did exactly that. Even heated the concrete with a tiger torch to get the butyl tape to stick really well. I got a drip still. I haven’t backfilled it yet as I bought more butyl tape to do it again this weekend and want a secondary seal. The seal land is so cheesy. It amazes me this is how they seal the things.
There may be a Sika product that can help as well - I have used their expanding grout to seal cracks in concrete. If I recall correctly, it uses capillary action to follow the moisture into the crack, and seal it up.
Anyone use Bentonite to seal a septic tank?
Linear Mode
