Water flowing back through percolation area into tank after rainfall

gunnerfitzy

Hi all,

On two occasions over the past 2 months, after major rainfall, my septic tank has backed up. After pumping out the second chamber I could see the problem... the water was gushing in from the outlet to the percolation area.

I don't think it's a problem with the percolation area itself I would say, it appears that the water table has risen as a result all the rain over the past months and a major rainfall then brings it up over the percolation area. The water then comes into the pipes and flows into the tank filling it up and pushing the waste water back up.

Has anyone any suggestions on how to deal with this? I could build a french drain around the perimeter of the property to divert the water however I have no where to divert the water to. I don't think that a newly constructed soak away could handle the amount of water that was flowing into the tank!

Any advice would be greatly appreciated.

Javan

You need better drainage, simple as that.

You should get advice on the current regulations (and they can vary from county to county). Many years ago when I had a similar problem the solution was to dig a new drainage trench. The new trench is fed by a submerged pump connected to a perforated pipe in a pebble bed, all of which is under a hedge so it gets drained in to the ground and through the hedge's root system.

As I say, that was many years ago. I would not be at all surprised if the current regulations did not allow any new builds with that sort of system.

A fella called fish

If you have a high water table then a percolation area is obviously unsuitable.

How is the surface water drained from roofs/hardstanding areas? Via a separate soakaway? If so, how is this currently performing?

gunnerfitzy

A fella called fish wrote: »

If you have a high water table then a percolation area is obviously unsuitable.

How is the surface water drained from roofs/hardstanding areas? Via a separate soakaway? If so, how is this currently performing?

The water from the roof is going to two separate soakaways. I've had no issues with those to date. That said, the roof is pretty small. It's a old two-bed cottage.

OBrother

If the tank has only backed up twice and never done this before, it could be that the soil under the percolation area has become clogged
and it needs to be moved to a new area. Moving it will in some Local Authority areas requires that you do a full site assessment under the current EPA code of practice.
The purpose of the percolation area is not only to distribute the effluent but also to allow the soil underneath it to provide additional treatment / purification, before it enters the ground water, for different sites and treatment systems the distance between water table and percolation trench will vary.
From my own experience moving the percolation area, and complying with the current code of practice may require you to lift the percolation area and use a pump from the tank to a new distribution box. This could have a big effect on your garden.

PaleRider

Try and manage until we know how the grant system will work. Is the system recently installed? How long was it working for prior to this problem? Is normal surface water getting away. Is your site very flat? Have you elevated areas that you can use. What size is your site? Can existing drains be lowered? Post a few photos? Is what you describe a percolation area? Their are options. Check out the site assessors registered with your local Co Council.