The whole house is built on a bog / underground river
This is why I spent $23K on screw piles and $18K on a ring beam suspended slab in order to build the house where we wanted to.
In order to stop moisture moving up through the concrete slab it is rated at MPA 32 instead of 25 and has a special moisture resistance additive
A network of subsoil drains, a sump and a sump pump keep the area around the house slab relatively dry in normal circumstances
However, after the extreme storms, this system was not able to deal with the amount of water and the sub soil water level has risen.
The area around the tank seems to consist of a water/sand slurry (ie quicksand) sitting in a clay basin
Hydrostatic pressure from ground water has caused the main vessel of the EcoMax system to move upwards by about 150 mm
I took some measurements using the laser level - the top of the puddle surrounding the main vessel is approx 200 mm higher than the creek (the only drainage point 25 m away)
We could certainly dig a trench to allow drainage of surface water from around the tank, down to the creek - but there are occasions where the creek will rise even higher and the drainage trench will run backwards
When we had our initial site meeting with Kevin, the Ecomax representative, we verbally informed him of the following facts
- The ground water level was very high
- We were having to use screw piles because we were building on top of a bog
- The neighbours had told us that on one occasion the creek had flooded 20 cm higher than the level we were standing on
It seems that he failed to take any notice of this information
At this stage I can only conclude that we have been sold a system that is inappropriate for this site.
Linda eventually managed to get Stuart, a representative of the company, to call us back
She tells me he became quite aggressive and essentially told her it was our fault for not providing enough drainage
Well I guess we could add more sub soil drains, sump pumps, drainage to the creek
However, it strikes me that all that is needed is for the water level around the vessel to rise 200mm above the outflow pipe for a short period of time and the vessel will rise.
Assuming a very conservative life span of 20 years for the Ecomax system - this implies that all we need is the creek to flood its banks any time in the next 20 year, or the sump pump to fail during a down pour and the Ecomax system will be destroyed.
This does not sound like a reasonable position to take.
Linda also tells me that he kept repeating that they had installed thousands of systems without any problems, and that the systems were built to an ISO standard.
I am very pleased to hear this - but I am not sure what the relevance of this is to our particular case where there obviously is a problem.
In fact we have already had a lot of problems with the system - see Fun & Games with supplier of Sewage System