Septic + percolation -> treatment system + polishing area, regs?

Lumen

Main question in bold for the tldr-ers.

I've a 4 bed 1980s house with an original and registered septic tank with a small, wrecked percolation area.

I want to bring it up to regs (not least to avail of the now increased 10k grant).

The site (0.8 acre total) is on a 10% slope with the house roughly centred on it, and I've up to 18m of clear lawn running down the slope at the back for the new system. I can't go near boundaries as there are trees everywhere (and the regs discourage it).

I think I understand the regs around percolation areas, being 18m of trench per person where people = bedrooms x 2, 2.5m centre to centre, 7m min distance from house, 18m max length of each trench etc

So I need 144m of percolation trench in total, e.g. 8x18m trenches covering 18mx20m.

But as I understand modern treatment systems, the area that the system drains into is called a "polishing filter" and doesn't need to be as large as a percolation area. Is that correct?

I can just about squeeze in 18m x 20m (8x18m trenches), or perhaps 15 x 25m (10x10m trenches) but as I'm looking to terrace the garden to produce a central flattish (3% slope) lawn area (over the percolation area) it'd be handy to go a bit smaller to accomodate the steps of the terraces.

Due to the sloping site I won't have issues with the water table, but I'm not sure how deep I can go before I hit bedrock, particularly if I'm re-grading the site.

I'm getting someone reputable to come on site and quote on Thurs but I'd like to tap the wisdom of boardsies before that.

Thoughts?

bfclancy2

https://www.boards.ie/discussion/2058353381/septic-percolation-treatment-system-polishing-area-regs

i have a polishing filter, installed 2018, six person treatment unit, takes up an area of around 10m by 10m, no trenches, network of perforated pipes laid on stone and covered in top soil

monseiur

You are fortunate that your site has a natural slope. Instead of opening separate trenches, just open up one area, the actual size area will depend on the depth. The deeper you can go the less area required to give the 'x' no of cubic metres required per person etc.

For example 7m. x 7m. x 1m. deep will give you a total of 49 cubic metres. 5m. x 5m. x 2m. deep will give you 50 cubic metres

Put a bed of 100 to 300mm clean pebbles under perforated pipes and cover with the same before finishing off with top soil otherwise you run the risk of soil blocking pipework over time and you'll be back to square on again.

Lumen

https://www.boards.ie/discussion/comment/122195472#Comment_122195472

Interesting and useful, thanks.

Can you cast any light on the regulatory elements? I could only find stuff from the EPA about linear measurements of percolation trenches, but you're talking about volumes of a polishing filter.

The EPA website says (my emphasis):

Who installs domestic waste water treatment systems?

A suitably qualified installer should install on-site waste water treatment systems. The supplier will usually recommend a person who is suitable to install the system, or they may install it themselves.  The installer is then responsible for testing the system to make sure that it is working effectively. The installation of the system should be certified.  Contact your City or County Council for more details as to their specific requirements.

Who certifies domestic waste water treatment systems

You can find out this in the Construction Products Regulation part of the Department of Housing, Planning and Local Government website. The manufacturer must draw up a declaration of performance and affix a CE marking to the product, following testing by a notified third party body. There are also obligations on importers and distributors to ensure the products they handle are compliant. You will find information on building product control and certification on the Department of Housing, Local Government and Heritage and the National Standards Authority of Ireland websites

That's a bit ****, because they slide from certification of an installation to certification of a product, which are obviously completely different.

Maybe I'm looking in the wrong place. I can't find anything on the Wicklow CC website about certification of upgraded systems, only stuff relating to planning permission and new builds.

monseiur

I'm afraid I'm not up to speed on Local Authority rules & regs. when it comes to septic tanks etc. But if your local authority is paying a grant for upgrade I assume that they have certain standards laid down in writing that you must satisfy before they pay. Have a chat with you local council planning/ environment engineer he/she should be able to give you the low down or guide you in the right direction.

Are you planning to replace your existing septic tank + polishing area or just the polishing are only. Opening up X no. of trenches in a confined area may seem OK on paper but not always practical for the excavator operator on site, where the width of the excavator is required between trenches. With the vibration etc the trench banks are liable to collapse. Excavating one big are, laying down the perforated pipes and joining to septic tank outfall then back filling is the better option. Be sure to leave an inspection chamber at septic tank outfall.

Lumen

Full system replacement.

I was told yesterday by potential supplier:

• Report your septic tank issues to the council, stressing urgency (mine are bad, so no need for exaggeration)
• Council inspects and tests flows from house, including greywater and stormwater, using dyes. We have a separate soak pit on the planning documents but that was almost 40 years ago so no idea whether it's still functioning.
• Council documents status quo and provides list of suppliers
• Quotes sought by homeowner, supplier provides design to council for approval
• Work is done with photos during process
• Documentary evidence of install provided to council, council visits to check they weren't spoofed for a grant
• Grant paid

As far as polishing filter is concerned, trenches aren't a thing any more, it's done with a continuous area as you and bfclancy2 have suggested.

The man suggested as small as 20sqm but bigger is better. I want to re-landscape anyway so 100sqm wouldn't be a problem other than cost.

I might spec a 10 person system for future proofing, assuming it doesn't cause an issue with the grant.

I'll be checking all this with the council asap.

My only remaining concern is smells. It would be convenient to locate it fairly close to the house only a handful of metres from a sitting area. Other than regular maintenance is there a particular type of system less prone to stink?

bfclancy2

https://www.boards.ie/discussion/comment/122204774#Comment_122204774

zero smell off my system, nothing at all, not even if you are sitting on the grass directly above the polishing filter