ᐅ Constructing a Soakaway on Your Property Yourself

We need to manage the rainwater infiltration ourselves. Should we do it ourselves or accept a quote from our construction company and a civil engineer? Both are around €6500 (approximately $7000). To save some money, I’m considering doing it myself. Recently, a colleague told me that you can build a soakaway system yourself using a water tank (see picture). He simply made holes for connection and infiltration. The galvanized steel frame would protect the tank from deformation. This is much cheaper than ready-made soak pits.

Is it possible to build a soak pit yourself like this? If so, how would you approach it and what do you need?

Thanks in advance

Best regards

Of course you can do that. It’s actually quite simple. However, it also depends on the type of system you want to install.

Rainwater infiltration systems require careful planning and calculation due to their dimensions. Then you need to decide which type of system you want to use. Collecting water first in a tank and letting the overflow seep into a soakaway? Are you even allowed to use tanks?

Hello Evolith,

According to the plan, four infiltration shafts are to be installed. The local authority does not specify any particular requirements, only that rainwater must infiltrate on the property. I was thinking of replacing the shafts with tanks in which I would create the holes for connection and infiltration myself. This is significantly cheaper. However, I wonder if this is acceptable or if these modified tanks are unsuitable for this purpose?

Thanks and best regards

Do you want to put anything into the tanks? For example, gravel?
I don’t understand why you wouldn’t just create a gravel bed once you’ve removed the soil. Why use those plastic things?

Do you know how many liters you need to secure? Then you don’t need to install 4 shafts/tanks; instead, you can bury a tank somewhere on your property (note that the larger tanks usually require 2 or 3 people to carry). These tanks often come with pre-made holes that you just need to "break open." You then connect an overflow from this tank, which leads into a soakaway / infiltration trench / similar system. Keep in mind that your driveway must also connect to this! So, place the tank thoughtfully or consider using a second smaller tank.

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

Since the whole system drains into a large garden area, we used an excavator with a 3-meter (10 feet) digging depth to dig a rectangular hole down to solid rock (sandstone). The hole was lined with geotextile fabric along the edges and filled with coarse drainage gravel up to 60 cm (24 inches) below ground level. Water is introduced there via a KG pipe (rigid PVC drainage pipe). Then another layer of geotextile fabric was placed on top and covered again with topsoil. Effectively, we went about 2.8 meters (9 feet) deep and chose a size of 3.5 meters by 3.5 meters (11.5 feet by 11.5 feet) for the larger one.

The KG pipe used for water inlet remains open at the end and features several large holes facing downward.

The dimensions of the soakaway pit depend heavily on the roof area and the infiltration capacity of the ground.