Seal new and old cisterns made of concrete or plastic

When constructing a cistern, sealing is only required for two-part and concrete manhole ring models. For monolithic cisterns and plastic versions, only inflows and outflows need to be sealed. It is not always possible to seal a leak in an already existing cistern.

New or old, plastic or concrete

There are four starting points that determine the procedure for sealing a cistern. There is a difference in the material from which the cistern was made. A plastic cistern is not repairable in all cases. With a concrete cistern a successful and permanent sealing is always possible.

A big difference is the sealing of new cisterns or the subsequent re-sealing of a leaky cistern. When it comes to a concrete cistern, sealing is promising in both cases.

New plastic cisterns

For new construction and expected external pressure sheathing
When a new plastic cistern no sealing work, since the container is inserted in one piece in the ground. Since the drains and inlets are located at the top of the tank, leakage through inadequate seals or connections is not possible.

With a high groundwater level, buoyancy forces can lead to damage and cracks in the tank container, which are very difficult to repair. If this circumstance or other reasons for soil distortions, such as in earthquake-prone regions, is known, a protective coating, for example of mortar, can prevent leakage.

Old plastic cisterns

If a leak has occurred in a plastic cistern, it can be closed by a special plastic welding process. Here, the hole or the crack with the same plastic "patched", which consists of the cistern. Fiber inserts can increase stability. The risk is usually whether the sealed surface is homogeneously connected to the environment. Since only one side can be welded, this is often not achievable.

New concrete tanks

For concrete cisterns, the type of sealing depends on the construction method. In manhole ring constructions, each joint between the superimposed rings and the cistern sole must be filled with a durable and waterproof mortar. In a two-part cistern only the patch head must be sealed so. However, the gap is usually above the maximum level of the water level. A one-piece monolithic cistern consists of a coherent component and does not need to be sealed.

Old concrete tanks

For sealing a concrete cistern, mud is typically used. The joints must be filled with suitable special mortar. Silicone or fountain foam is less suitable since the sealing sludge will adhere to it insufficiently. According to the manufacturer's instructions, the sealing slurries are applied in two to three layers on all inner surfaces of the cistern.

Tips & Tricks

Although some manufacturers advertise with bituminous or other resin-based sealants, you should prefer to sludge. Thus, the air and evaporation environment of the cistern remains unchanged.

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