Build a cesspit on your property yourself

We have to take care of the rainwater infiltration ourselves. Do it ourselves or accept an offer from our construction company and a civil engineer? Both are around €6500. To save some money, I wanted to do it myself now. Recently, a coworker told me that you can build the infiltration system yourself from a water tank (see picture). For this, he simply made holes for the connection and infiltration. The galvanized steel frame would protect the tank from being compressed. This would be much cheaper than finished infiltration pits.

Is it possible to build such an infiltration pit yourself? If yes, how would you proceed and what is needed for it?

Thanks in advance

Regards

Of course you can do that. It's actually quite simple. But it also depends on what kind of system you want to make. Rainwater infiltration needs to be well planned and calculated because of the dimensions. Then you have to decide what kind of system you want to use. Catch it first with a tank and let the overflow infiltrate into a soakaway? Are you even allowed to use tanks?

Hello Evolith

According to the plan, four soakaway pits are to be made. The municipality does not specify anything, only says that rainwater must infiltrate on the property. I wanted to replace the pits with these tanks where I myself make the holes for the connection and the infiltration. It is just much cheaper. I just wonder if that is possible or if the converted tanks are unsuitable for that?
Thanks and regards

Should something still be put into the tanks? Like, for example, gravel? I don’t understand why you don’t just make a gravel bed straight away once you’ve removed the soil. Why the plastic things?

Do you know how many liters you need to secure? Then you don't need to make 4 shafts/tanks, instead you bury a tank somewhere on your property (note the large ones are often only manageable by 2 or 3 people). These tanks usually have pre-made holes that you just need to "tear open." Then you connect an overflow to this tank, which leads into a soakaway pit / infiltration trench / something similar. Be careful, your driveway must also connect there! So place the tank well or consider using a second smaller tank.

Regardless of the correct sizing, I have already built two soak pits. one with and one without a preceding buffer cistern / buffer tank.

Since the whole thing drains into a large garden area, we each dug a rectangular hole with an excavator with a 3m digging depth down to the solid rock (sandstone), lined the edges with geotextile fabric, and filled it with coarse drainage gravel up to 60cm below the ground surface. Water is introduced there via KG pipe. Then geotextile fabric on top and covered again with topsoil. Effectively, we went just under 2.8m deep and chose 3.5m x 3.5m for the large one.

The KG pipe for introduction remains open at the end and is provided with several large holes pointing downward.

The size of the soak pit depends heavily on the roof area and the infiltration capacity of the substrate