Septic tank or treatment plant.

[tonyandalana]

Been trying to get an answer from DEFRA but they don't exactly rush to respond. I live in a rural area of Cornwall where our property has a septic tank which was installed about 20 years ago. It works perfectly and the drain field is entirely on our own property. The tank is however situated only about 10 feet from our boundary with our neighbour. However there are no problems with the system. Also it's worth noting that there are no streams or springs anywhere near. A builder has advised me that our septic tank will not conform to upcoming legislation and says we need to install a treatment plant.
If that is true then I will bite the bullet but I'm just trying to find out whether the builders information is correct. Any advice would be greatly appreciated. Thanks.

 

[Sambostar]

Been trying to get an answer from DEFRA but they don't exactly rush to respond. I live in a rural area of Cornwall where our property has a septic tank which was installed about 20 years ago. It works perfectly and the drain field is entirely on our own property. The tank is however situated only about 10 feet from our boundary with our neighbour. However there are no problems with the system. Also it's worth noting that there are no streams or springs anywhere near. A builder has advised me that our septic tank will not conform to upcoming legislation and says we need to install a treatment plant.
If that is true then I will bite the bullet but I'm just trying to find out whether the builders information is correct. Any advice would be greatly appreciated. Thanks.

Bit late, but I'm in a similar situation with a septic tank replaced in 1993, 4 metres away from a habitable area in a building built at the same time, although it did have a 14' footing on that corner to pass Building Control (That was the old brick septic tank location) and CONFORMED with the Building Regulations (1989) at the time it was installed. We were given advice by the estate agent in 2020/21 odd (After the hype of the new Part H of the Building Regs) that our septic has to conform to EN 12566, which being installed in 1993 it obviously doesn't and that any foul discharge to groundwater is now illegal and it must be replaced with a treatment plant.

All of these facts are false. The new legislation only concerns septic tanks that are discharging FOUL WATER to WATERCOURSES or ditches or septic tanks whose drain fields have failed, so that stink and sewerage is evident on the surface of the soil, in which case new drainage fields have to be constructed that work. If the tank met Building Regulations WHENEVER it was installed and the drainage field works adequately well, it is absolutely fine and does not need replacement as far as the Regs are concerned. Pisses me off that so many people are making work for themselves by misleading the public about the new regulations and I'm sure estate agents are either lazy or in a racket with treatment plant installers (Many of whom's work I've seen is absolutely shocking and would fail the standards, no disrespect to the many that do an excellent job)

The only exceptions are that you have very heavy soil, liable to flooding and so you are obviously failing porosity tests for a new drainage field, THEN the only option is a treatment plant, the discharge from which you will then have to run into a leachfield drainage system (Basically doesn't matter if it is waterlogged as a treatment plant discharges 'Clean' water. The other exception is that you produce more than 2 CUBIC METRES of discharge per day (Use the DAILY DISCHARGE CALCULATOR) to work out your discharge, in which case, again you will need a treatment plant. According to the new legislation you have an EXISTING DISCHARGE (Pre 2015) and if it works OK and is adequate for the number of bedrooms/habitants (If you want to sell) and meets these other two criteria above, then if you are selling the place, all you need do is instruct the new owners with a notice of instruction for the system and it is perfectly good and legal.

I've included the latest Regulations, including a bit by a leading estate agent and British Water.

https://www.gov.uk/government/publications/sewage-discharges-calculator-for-domestic-propertieshttps://assets.publishing.service.g...achment_data/file/442889/BR_PDF_AD_H_2015.pdfhttps://www.gov.uk/guidance/general-binding-rules-small-sewage-discharge-to-the-groundhttps://www.struttandparker.com/kno...mpliant-with-the-2020-septic-tank-regulationshttps://www.britishwater.co.uk/news...c-tanks-regulations-information-statement.htm

 

[Sambostar]

Also, I'II just add, if a porosity test fails for septic tank field drainage, due to a high water table or bad soil impermeability AND a nearby watercourse or ditch is not available, not only do you need a treatment plant and soakaway, but you also need to get a PERMIT FOR CONSENT TO DISCHARGE from the Environment Agency, as you are effectively discharging straight to groundwater, without any water holding on site. Hope that is all clear.

To do a porosity test, dig a 300mm x 300mm hole below the proposed bottom level of the drainage pipe. Fill with water - Day 1. Day 2 - fill again and record time in seconds for the water to drop from 75% full to 25% and divide by 150(mm) to get a Vp (Average time for water to drop 1mm). Vp MUST be between 15 and 100 (Seconds/mm). Not too fast or too slow essentially. If this Vp is NOT achievable you MUST install a water treatment plant instead of the Septic Tank (Existing or Newly Installed). Essentially if it takes over 4 hours and ten minutes (15,000 seconds) to drain from 75% to 25%, you're buggered as 15,000/150 = 100, so you'll have to install a treatment plant AND most probably get a discharge licence from the Environment Agency unless you have enough room at the property for an adequate drainage field (See below).

To work out drainage field size for a Septic Tank the Area (A) = V x P x 0.25, where (P) is number of people it serves. If there is NOT enough space for a Septic Tank soakaway within the property, then a Treatment Plant MUST be installed

For a treatment Plant A = V x P x 0.20 However if this area is also not achievable, then you have to work with what you have and advise the Environment Agency, you will need a licence from them anyway. It's not like a few million properties will be condemned or anything.

This all for the UK btw!