Soakwell Repairs - Sinking Paving
What causes paving to sink?
If your paving is sinking around your soakwell it is more than likely an issue with the volume. It is extremely common for soakwells to be installed without any calculation having been performed. The volume of water fills up the soakwell and can draw sand in, between the soakwell and the cover, particulary if not wrapped in geofabric or the inlet was not sealed.
If the volume is not the issue there is likely a hole in the soakwell or a gap between the cover and the soakwell, both issues would be prevented by wrapping the soakwell in geofabric during installation
What's the solution to sinking paving?
The key to preventing this issue is to perform a soakwell volume calculation based on the catchment area. The catchment area is the impervious surfaces (roof or ground area) in m2 that the soakwells will be catering for.
Once you know the volume there are two options, either supplement the existing soakwell or install a new one. Generally if the existing soakwell is a plastic 600 x 600 we will remove it and start fresh.
If the issue is gaps then then they may be fixed by either adding geotextile fabric or mortaring the gaps.
We recommend using grates under downpipes instead of direct connections as it is critical that the system can breath and any overflow will happen on the ground, not in the roof.
Sinking Paving Summary
Sinking paving is generally caused by inadequete volume.
When the soakwell fills up it draws in sand through the inlet and cover if not sealed (causing the sinking).
The solution is to perform a calculation based on the roof area and council formula to detemine the soakwell volume recommended.
One solution is interconnect a new soakwell to the existing one to make up the volume. Generally this is only done for larger soakwells.
The preferred solution is to remove the old and install a new, trafficable, modular ploypropylene soakwell. These are wrapped in geofabric and totally sealed.
How to prevent sinking paving around a Soakwell ?
There is no point repairing the paving or trying to fix the existing soakwell if the volume is inadequete, the issue will re occur. There are two options to permanantly solve this :
Supplement Existing Soakwell Volume
If there is adequete space and the existing soakwell is good quality then it can be retained. Once the required volume is determined the existing soakwells volume is simply subtracted from the total.
The remaining volume is provided by an interconnected row of modulars soakwells, positioned at least 1m away from the existing soakwell.
Replace with a new Soakwell
Generally a number of our modular 140 litre soakwells will be installed with out 1t excavator (720mm wide) as an interconnected line. These are fully trafficable, totally wrapped in geofabric and extremely efficient with a total void area of over 60%. They are perfect for established homes, where space and access is at a premium.
Installing a new soakwell is often preferred for a number of reasons.
- If the existing soakwell is interconnected to other soakwells it is impossible to determine the volume provided. Starting fresh insures no future issues.
- If the original soakwell is poor quality, such as a plastic 600 x 600 soakwell from Bunnings, then retaining it simply introduces unnessecary failure points, particulary given the cost of a single polypropylene soakwell.
- By starting fresh you can have full confidence that the issue is solved. In 11 years of installing soakwells we have had zero issues with sinking paving by following these basic principles.
Sinking Paving Summary
Sinking paving is generally caused by inadequete volume.
When the soakwell fills up it draws in sand through the inlet and cover if not sealed (causing the sinking).
The solution is to perform a calculation based on the roof area and council formula to detemine the soakwell volume recommended.
One solution is interconnect a new soakwell to the existing one to make up the volume. Generally this is only done for larger soakwells.
The preferred solution is to remove the old and install a new, trafficable, modular ploypropylene soakwell. These are wrapped in geofabric and totally sealed.