Regarding the always thorny subject of sewerage treatment.
I describe it as thorny because it always involves upheaval and cost. Heres an explanation of a typical problem which we see four or five times a year and what I recommend.
The sewerage system fills up with water very soon after it has been emptied or you notice a problem when you return to your holiday home after being away.
Most people don’t know and don’t want to know where their sewage system is or how to look inside it to check the levels. The call someone out to empty the tank but what happens if it fills up again quickly. How do you fix the problem ?
Repair, Replace or Renew ?
If you have made sure surface water (rain water) is not going into the cesspit it can only be that ground water is getting in below ground. This is a common problem here because people try and build the cheapest cesspits that they can. Usually from interlocking concrete rings ( like massive drainpipes stacked on top of each other ) They don’t seal the joints and occasionally the poorly educated builder would have knocked holes in the bottom “so that the liquid will drain”
Liquid from a septic tank should be lead away into what is called a drain field (more of that later)
The unsealed joints and holes knocked into the walls of the cesspit allow water at underground pressure to enter the space inside the tank as the air pressure inside is lower.
Bearing in mind that a cesspit is a sealed tank which should be emptied once a year. The only way to make it work properly is to have it sealed or replaced.
Sealing is very difficult to do. Even when empty there can be dangerous levels of gas present. Making working inside the tank dangerous.
Because there is a lot of fat in sewerage it makes it almost impossible to make a sealing product stick to the internal walls and joints. Cleaning the fat out of the pores of the concrete will be expensive, difficult and time consuming.
The water that is currently entering the tank will continue to do so especially when the tank is empty to enable work.
My recommendation is to replace the tank. With what ?
You could in theory fit a smaller set of interlocking concrete rings mounted correctly inside the existing leaking walls. The bottom of the cesspit would have to be thoroughly emptied as you cant lay concrete on top of lightweight material (poo !). You would also have the problem of dangerous levels of gas present. Making working inside the tank dangerous.
Or you could dig up the existing tank and replace it with a fiberglass (no ground water can enter) two chamber sewerage treatment tank or digester as they are known. The water which runs off these tanks is fairly clean and is passed to a “drain field” which is a maze of perforated pipes which allows the water to seep slowly into the ground over a wide area. Because the pipes are perforated you don’t usually get rain water passing up them into the digester tanks.
