Percolation Area Shape

rampantbunny

Hi all. I'll be starting a new build sometime this year (or so I keep telling myself).
I've had a brief perusal of the EPA guidelines for percolation area design and also noted my own EPA report.
I need a 'polishing filter of 140m, which on my plans is shown as 7 parallel runs of 20m each.

For aesthetic and cost reasons we're looking at relocating the percolation area (pending planning acceptance). The candidate area does not allow for 7 parallel runs although there is area for longer runs (but less of them). Plus the candidate area is not 'square'.

Questions:
Given that 140m is specified on my report, does this mean the polishing filter could be constructed of 4 x 35m or 5 x 28m etc? i.e is there a certain amount of flexibility? (I note on the EPA guidelines that 18m max is specified).

Does the polishing filter need to be square\rectangular? Or could it be like the following or a variation?

===============
......====================
.......===============
.........============

Ignore the dots. They are there because the editor strips the leading spaces.

(I did read somewhere that the ends are to be joined and vented so not sure the above allows this easily).

Poor Uncle Tom

Your post seems a little bit all over the place.

First things first are you referring to a polishing filter or a percolation area?

20m is the maximum length of percolation piping allowed in any trench run, and 10m is the maximum piping run for polishing filter piping. Also generally, polishing filter piping is not vented as it works on a pressurised system.

rampantbunny

Hi Tom (PUT).
My interpretation of my EPA report is obviously bad..much bad
On this doc I see a section 'polishing filter' with an entry of 140m.

If I look at my site layout I see 7 parallel lines each 20m in length, therefore 140m. So I've reconciled the available figures incorrectly.

I do see on the plan that the 7 lines are collectively labelled "percolation trench".
But nothing on my EPA report for this. Would you expect to see a figure for this on the EPA report?

Ultimately it is the percolation area I'm looking to relocate.

Poor Uncle Tom

Your first port of call about relocating a percolation area should be to contact the person who carried out the Site Assessment and ask their advice, ultimately your percolation area will have to be signed off by an approved indemnified assessor, this can only be done if the works being carried out complies with the site assessment and this can only be done with the say so of the site assessor involved.

rampantbunny

Tom, thanks for the response and I do appreciate it.

My first port of call is not necessarily a return to the designer, not before I at least try to educate myself here on boards.
So, my queries still stand re. shape\layout if anyone can advise.

Just to add that all t's will be crossed with respect to compliance. I'm not looking to do anything to contravene regs etc.

muffler

rampantbunny wrote: »

Tom, thanks for the response and I do appreciate it.

My first port of call is not necessarily a return to the designer, not before I at least try to educate myself here on boards.
So, my queries still stand re. shape\layout if anyone can advise.

Just to add that all t's will be crossed with respect to compliance. I'm not looking to do anything to contravene regs etc.

Actually you will have to go back to your site assessor. Each site is different and there is no "one size fits all" when it comes to specifying an appropriate type of sewage treatment and disposal system.

No one here knows what your site looks like, what features are there, water table levels, soil makeup etc etc etc. So as your query is very site specific then you will have to go to the only person who has access to all the relevant info.

Poor Uncle Tom

rampantbunny wrote: »

Tom, thanks for the response and I do appreciate it.

My first port of call is not necessarily a return to the designer, not before I at least try to educate myself here on boards.
So, my queries still stand re. shape\layout if anyone can advise.

Just to add that all t's will be crossed with respect to compliance. I'm not looking to do anything to contravene regs etc.

Didn't mean to come across as abrasive, but as muffler has pointed out the only person with the required information on your site to answer questions on relocation of the percolation area is the Site Assessor.

Your other questions:
Shape: Rectangle, square, rhombus or parallelogram are all acceptable. Trapezium is not acceptable.

Length: Maximum trench length 20m and 2.5m centres.

rampantbunny

muffler wrote: »

Actually you will have to go back to your site assessor. Each site is different and there is no "one size fits all" when it comes to specifying an appropriate type of sewage treatment and disposal system.

No one here knows what your site looks like, what features are there, water table levels, soil makeup etc etc etc. So as your query is very site specific then you will have to go to the only person who has access to all the relevant info.

I agree Muffler. No denying I have to go back to assessor at some point. But not before I have an idea myself or I'll possibly be swamped (no pun) with information.

Re. the one size fits all; I'm taking it from Uncle Toms later post that my site characteristics have no impact on this in relation to shape of perc. area, nor any impact on the division of run lengths i.e. even though design of the system is very specific, these two aspects in question are not, they are definitive.

Are you maybe saying that the characteristics of my site could impact these?

rampantbunny

Poor Uncle Tom wrote: »

Didn't mean to come across as abrasive, but as muffler has pointed out the only person with the required information on your site to answer questions on relocation of the percolation area is the Site Assessor.

Your other questions:
Shape: Rectangle, square, rhombus or parallelogram are all acceptable. Trapezium is not acceptable.

Length: Maximum trench length 20m and 2.5m centres.

Nothing abrasive about your posts at all Tom. No need to qualify anything. Thanks for the info.

Poor Uncle Tom

rampantbunny wrote: »

Re. the one size fits all; I'm taking it from Uncle Toms later post that my site characteristics have no impact on this in relation to shape of perc. area, nor any impact on the division of run lengths i.e. even though design of the system is very specific, these two aspects in question are not, they are definitive.

You may not be taking me up correctly.

For instance, your percolation area is 7 No. trenches x 20m each giving a total of 140m of percolation area designed on your site suitability assessment.

Your Site Assessor chose to design your system that way, for whatever reason. It would be perfectly acceptable, under the EPA's code of practice, to fit a system with 10 No. trenches each being 14m in length. However, eventhough this would comply with the EPA's code of practice, it may not be acceptable to the assessor who has to sign off on the works, as there may have been another reason, such as separation distances, to use the specific design called up on the Site Assessment.

So the concept of 'one size fits all' has no place here and it wasn't my intention to get that message across.

Also, if you move the percolation area you may need a new percolation test which could result in a different overall trench length being required in the new location.

muffler

rampantbunny wrote: »

Are you maybe saying that the characteristics of my site could impact these?

That's a possibility, yes.

rampantbunny

Poor Uncle Tom wrote: »

You may not be taking me up correctly.

For instance, your percolation area is 7 No. trenches x 20m each giving a total of 140m of percolation area designed on your site suitability assessment.

Your Site Assessor chose to design your system that way, for whatever reason. It would be perfectly acceptable, under the EPA's code of practice, to fit a system with 10 No. trenches each being 14m in length. However, even though this would comply with the EPA's code of practice, it may not be acceptable to the assessor who has to sign off on the works, as there may have been another reason, such as separation distances, to use the specific design called up on the Site Assessment.

So the concept of 'one size fits all' has no place here and it wasn't my intention to get that message across.

Also, if you move the percolation area you may need a new percolation test which could result in a different overall trench length being required in the new location.

No Tom, I've grasped it but my post to Muffler was very poorly phrased when referring to the division of the total run length and this not being impacted by site characteristics. My fault.

And, as indicated, the assessor will be contacted and have final say but I feel better equipped now.

A final question if you are not feeling overcooked on this subject: max trench length = 18m from the distribution box.
Is it permitted under the guidelines\regs to have an 18m run either side of the distribution box giving a total run of 36m in a straight line?

Poor Uncle Tom

rampantbunny wrote: »

Is it permitted under the guidelines\regs to have an 18m run either side of the distribution box giving a total run of 36m in a straight line?

If done correctly then yes, but it is not considered one run of 36m but two runs of 18m each......;)

yoloc

Poor Uncle Tom wrote: »

Your post seems a little bit all over the place.

First things first are you referring to a polishing filter or a percolation area?

20m is the maximum length of percolation piping allowed in any trench run, and 10m is the maximum piping run for polishing filter piping. Also generally, polishing filter piping is not vented as it works on a pressurised system.

Is there a minimum pipe run in a percolation area and aren't you suppose to have 1 run per bedroom in a house. The reason i ask this is that i worked on a percolation area for a 5bed house + 1 study for my wife's brother and there was only four 6m runs and a 6m run at the bottom connecting them all. His land had good drainage hence only 30m of pipe.

In this same percolation area, it had a pipe from the house connected to the septic tank, a pipe coming out of septic tank about 1m then a 90degree bend with a pipe of 1m into a perc box and only 1 pipe coming from the percolation box running 25m to the perc area then T'd off into the 4 runs.

Thought id put this in here seeing as its about the same thing and didnt really want to start a thread because only needed the question answered rather than a whole thread. Hope its OK OP

yoloc

Poor Uncle Tom wrote: »

Length: Maximum trench length 20m and 2.5m centres.

Is it not suppose to be 2m centres or have the regs changed

Poor Uncle Tom

The maximum length mentioned above is the TRENCH length not the PIPE length. The maximum pipe length is 18m plus freeboard = 20m maximum trench length mentioned above.

The distance between trenches is 2m and the trench width is 500mm which means the distance from centre of trench to centre of trench is 2.5m.

yoloc wrote: »

Is there a minimum pipe run in a percolation area and aren't you suppose to have 1 run per bedroom in a house.

There's no minimum length but I would imagine that one pipe length of 6m plus free board would be the minimum trench length, that would be 8m, but there's nothing specific written.

It's up to the site assessor to specify the percolation trench length, it's not down to any rule of thumb like one trench per bedroom.

yoloc wrote: »

The reason i ask this is that i worked on a percolation area for a 5bed house + 1 study for my wife's brother and there was only four 6m runs and a 6m run at the bottom connecting them all. His land had good drainage hence only 30m of pipe.

What was the T value for the site tests and what was the system designed to, SR6 or COP? 30m for that size of house seems way undersized.

yoloc wrote: »

In this same percolation area, it had a pipe from the house connected to the septic tank, a pipe coming out of septic tank about 1m then a 90degree bend with a pipe of 1m into a perc box and only 1 pipe coming from the percolation box running 25m to the perc area then T'd off into the 4 runs.

That doesn't comply with SR6 or the COP.

yoloc wrote: »

Is it not suppose to be 2m centres or have the regs changed

SR6 1991 had trenches at 2m centres.
EPA Code of Practice have trenches at 2.5m centres.

Following 2010 legislation only the Code of Practice applies to new works which got planning permission after August 2010.

yoloc

Poor Uncle Tom wrote: »

The maximum length mentioned above is the TRENCH length not the PIPE length. The maximum pipe length is 18m plus freeboard = 20m maximum trench length mentioned above.

The distance between trenches is 2m and the trench width is 500mm which means the distance from centre of trench to centre of trench is 2.5m.



There's no minimum length but I would imagine that one pipe length of 6m plus free board would be the minimum trench length, that would be 8m, but there's nothing specific written.

It's up to the site assessor to specify the percolation trench length, it's not down to any rule of thumb like one trench per bedroom.


What was the T value for the site tests and what was the system designed to, SR6 or COP? 30m for that size of house seems way undersized.



That doesn't comply with SR6 or the COP.



SR6 1991 had trenches at 2m centres.
EPA Code of Practice have trenches at 2.5m centres.

Following 2010 legislation only the Code of Practice applies to new works which got planning permission after August 2010.

What does mean when you say freeboard


T values was 9-10mins, 30m of pipe sr6. The pipe runs are 4 runs of 6 + 1 run at the bottom connected to the 4. Why does the house seem oversized. This was approved by the planners back in 2005.


As for the percolation box not complying with sr6. If he were ever to sell it, would this be a major problem or would it just be a case of moving the percolation box to nearer the percolation area. How far can the box be away from the septic tank and distance from the percolation area.

Poor Uncle Tom

yoloc wrote: »

What does mean when you say freeboard

Bad choice of words, sorry.
Basically the pipe doesn't end at the 'clay', it ends on gravel. There is gravel at each end of the pipe as well as at both sides and beneath and above the pipe. The total maximum length of trench is 20m (18m of pipe).

yoloc wrote: »

T values was 9-10mins, 30m of pipe sr6.

The details in SR6 were based on a standard 6 person dwelling house (that's only from memory so I'm open to correction on it as I don't have my copy to hand) The SR6 worked on 2 persons per double bedroom and 1 person per single bedroom. Allowances would need to be made for the 5 bedrooms and 1 study house.

yoloc wrote: »

The pipe runs are 4 runs of 6 + 1 run at the bottom connected to the 4.

Using the end run is not allowed under SR6.

yoloc wrote: »

Why does the house seem oversized. This was approved by the planners back in 2005.

As I've said above it would be normal to allow for the house being above average size in the percolation area.

Regardless of whether the LA granted planning permission for it or not, the onus is on the owner to ensure it is built in compliance with the regulations.

yoloc wrote: »

As for the percolation box not complying with sr6. If he were ever to sell it, would this be a major problem or would it just be a case of moving the percolation box to nearer the percolation area.

It's a simple case of it was either designed in compliance with the regulations or it wasn't and then a case that it was either constructed in compliance with the design or it wasn't.

Then there is the question, why is it not constructed in compliance with the regulations?

yoloc wrote: »

How far can the box be away from the septic tank and distance from the percolation area.

How far was it granted planning permission away from the septic tank and from the percolation area?

yoloc

Poor Uncle Tom wrote: »

The details in SR6 were based on a standard 6 person dwelling house (that's only from memory so I'm open to correction on it as I don't have my copy to hand) The SR6 worked on 2 persons per double bedroom and 1 person per single bedroom. Allowances would need to be made for the 5 bedrooms and 1 study house.

The 5 bed house is a 2x double room and 3 single.

Poor Uncle Tom wrote: »

Using the end run is not allowed under SR6.

His engineer left him to do the work himself and told him that all he needed was 30m of percolation pipe. Over the phone he said 4 runs with a run at the bottom would do. 

Poor Uncle Tom wrote: »

It's a simple case of it was either designed in compliance with the regulations or it wasn't and then a case that it was either constructed in compliance with the design or it wasn't.

It was designed in compliance but dont think it was constructed to compliance but dont think it would take much to correct.

Poor Uncle Tom wrote: »

How far was it granted planning permission away from the septic tank and from the percolation area?

I checked the planning online and it doesnt say how far from septic tank but shows a 20m line from house to percolation area.







13m away from house
House

---

(septictank)
. ! .
. ...................................................box
........................................................I
. ..................................................... I
........................................................I
....................................................... I
........................................................ I 23-25m pipe run
.........................................................I
.........................................................I
...........................................

---

...........................................I.........I.........I.........I
...........................................I.........I.........I.........I
...........................................I.........I.........I.........I 6M perc pipe runs
...........................................I.........I.........I.........I
...........................................I.........I.........I.........I
...........................................I.........I........I..........I
...........................................___________________ 6m run perc pipe



If this is his percolation area, IMO all he has to do is put the percolation box where it T's off and add another 1.5m of pipe to the end runs and do away with the bottom percolation pipe. Will he need to apply for new planning for this or just fix without it. As for the percolation area, there has been a family of 6 living in it, him,his wife,3 kids and a grand parent and there doesnt seem to be any signs that its not percolating properly.

muffler

yoloc please use quote tags instead of multi coloured lines of text. Thanks

Poor Uncle Tom

yoloc wrote: »

His engineer left him to do the work himself and told him that all he needed was 30m of percolation pipe. Over the phone he said 4 runs with a run at the bottom would do.

Has the system been certified? 

yoloc wrote: »

It was designed in compliance but dont think it was constructed to compliance but dont think it would take much to correct.

yoloc wrote: »

I checked the planning online and it doesnt say how far from septic tank but shows a 20m line from house to percolation area.

It should be scalable from the Site Layout Plan.

yoloc wrote: »

IMO all he has to do is put the percolation box where it T's off and add another 1.5m of pipe to the end runs and do away with the bottom percolation pipe.

And you say this with full knowledge of the SR6?
Is the Septic Tank location acceptable under SR6 1991?

yoloc wrote: »

Will he need to apply for new planning for this or just fix without it.

A very good question. A lot will depend on when the original planning permission was granted, is the permission expired for carrying out works?

yoloc wrote: »

As for the percolation area, there has been a family of 6 living in it, him,his wife,3 kids and a grand parent and there doesnt seem to be any signs that its not percolating properly.

You have no means of knowing what is happening beneath the ground, all you can see is what's on top of the ground. How long is the percolation area in place? is there permission for a reserve percolation area.

rampantbunny

yoloc wrote: »

.... answered rather than a whole thread. Hope its OK OP

I've no problem with it Yoloc.

yoloc

Poor Uncle Tom wrote: »

Has the system been certified? 

TBH, not sure.

It should be scalable from the Site Layout Plan.

Never thought about that

And you say this with full knowledge of the SR6?
Is the Septic Tank location acceptable under SR6 1991?

See below
How far from house does teh tank have to be in SR61991

A very good question. A lot will depend on when the original planning permission was granted, is the permission expired for carrying out works?

Its well expired, 2004/5 when the planning was approved so probably run out in 2010

You have no means of knowing what is happening beneath the ground, all you can see is what's on top of the ground. How long is the percolation area in place? is there permission for a reserve percolation area.

Its been in place from 2004/5. The house was started april of that year and finished sept of that year. All the pipes where laid to the proper fall and never was any of the vent pipes/perc box holding water so it must be percolating properly.



http://www.google.com/url?sa=t&rct=j&q=sr61991%20percolation%20area&source=web&cd=2&cad=rja&ved=0CFIQFjAB&url=http%3A%2F%2Fwww.ambill.net%2FBIO_CLEANER%2FPercolation_Area_Design.html&ei=pycbUtSRNaWN7Qbi9oCYCQ&usg=AFQjCNGFQLyw3Z-9spGQSGswaaaJi9bZ6A&bvm=bv.51156542,d.ZGU

SR61991

PERCOLATION AREA DESIGN NOTES
INTRODUCTON
These recommendations deal with the BC 8 Wastewater Treatment plants used to treat and dispose of domestic sewage from Single Dwelling Houses. All procedures and recommendations outlined below are as outlined in THE NATIONAL STANDARDS AUTHORITY OF IRELAND'S publication SR6 1991 SEPTIC TANK SYSTEMS, RECOMMENDATIONS FOR DOMESTIC EFFLUENT TREATMENT AND DISPOSAL FOR A SINGLE DWELLING. It should be the responsibility of the builder that all construction work on the percolation area should be in strict accordance with the recommendations contained in the publication and any subsequent recommendations.

The uPVC pipe for the BC 8-treatment plant to the percolation area should be watertight and be 100mm nominal diameter laid to 1 in 60 fall. This pipe should terminate in a 600mm by 600mm distribution box from which the distribution pipes for the percolation area will begin. The distribution box should evenly distribute the effluent the distribution pipes in the percolation area.

Location of Percolation area

Sites should preferably be level well-drained areas, or, on convex slopes. Sites that are in depressions, at the bottom of slopes or on concave slopes should be avoided.
Percolation areas should be located at furthest point away from groundwater sources of drinking water.

Refer to table below for suggested distance between a well and a percolation area.

(Table 1)

Type of Soil Minimum dept of subsoil above
rock (m) Minimum depth of water table
(m) Minimum Distance from percolation
area (m)
Clayey till, silty clay, clay where
(low percolation rate)
'T' more than 30
1.0
1.0
30.0
Sandy clay, sandy till
(medium percolation rate)
'T between 15 and 30
1
2 to 5
5
1
1
1
45
30 to45
30
Sand and Gravel ( high percolation rate)
'T' less than 15
1
2 to 5
5
1
1
5
60
40 to 60
30

Also the following conditions should be followed when siting a percolation area.
1. Preferably they should be located to the rear of a housing development furthest away from road.
2. No part of the percolation area should be within 20 m of the nearest dwelling house
3. No part of the percolation area should be within 3 m of the boundary of the adjoining site.
4. No water mains or service pipes should be located within the percolation area
5. No access roads, driveways, or paved areas should be located within the percolation area.
6. No part of the percolation area should be within 10 m of the nearest road boundary, stream or ditch

Size of Percolation Area

The size or area of the percolation area is dependent on the results of the percolation tests carried out on the site of the percolation area. Refer to the standard test sheet for determining the 'T' value for the site. The 'T' value is the time in minutes for a 1" or 25mm drop in the water level in the test hole(s)

The relationship between the value of 'T' and the length of distribution piping required for the percolation area is as given in Table 2.
(Table 2)

Value of 'T' Length of piping (m)
From 5 up to 10
Above 10 and up to 15
Above 15 and up to 30
Above 30 and up to 60
30
36
48
96

Note 'T' values less than 5 may indicate that the percolation rate is too fast possibly polluting the groundwater
'T' values greater than 30 may indicate that the percolation rate may be too slow and leading to ponding of the effluent at the site of the percolation area. Where this occurs a raised percolation area may be necessary. Recommendations for its construction are in appendix A attached.

Percolation Area Distribution pipes

o Pipe should preferably be 110mm diameter perforated smoothwall plastic drainage pipes with perforations of 8mm diameter at about 75mm centers along the pipe at about 4, 6 and 8 o'clock positions.
Note: Wavin Plastics supply these pipes

Percolation area Construction

- The pipe trenches shall be set out at 2 m centers
- The percolation pipes should be laid in trenches at least 450mm wide and bedded on 250mm depth of crushed stone (20 - 30 mm in size)
- Pipes should be laid to fall of 1 in 200 approx.
- Pipes should be interconnected at end of pipe runs
- Once the drainage pipes are in place they should be surrounded and covered to a depth of 150mm of crushed stone which should extend the full width of the trench
- Before the trenches are backfilled with the topsoil the crushed stone should be covered with peat fiber, geotextiles or similar permeable or durable materials. This is to prevent the stone being silted up with topsoil.

Maintenance of Percolation area

The percolation area should be inspected periodically and any signs of malfunctioning noted. This will show itself by obvious sings of blockage at distribution box, ponding, smell or pollution in the surrounding area. In this event contact our sales office. A reserve percolation area may have to be constructed.

BryanF

Its well expired, 2004/5 when the planning was approved so probably run out in 2010

there you go - best to consult an engineer who is on the local authorities site assessment register

yoloc

BryanF wrote: »

there you go - best to consult an engineer who is on the local authorities site assessment register

I agree but i also don't see the point in paying someone if the pipes where all laid to the proper fall, perc area in the right location and 85% built to SR61991 and there has never been 1 problem with this area. All i see that needs done is the distribution box needs moved and connected to all 4 pipes, another 1.5m added to the end of the pipe runs.

yoloc

cant see that post staying for to long lol. Dont think your aloud to advertise on here <SNIP>

muffler

yoloc you almost got the quote tags right. Just omit the forward slash (/) from the tags at the the start of the text. I'll tidy that up for you now.

When replying to a post that you wish to break down into individual sections you can also just highlight the sections individually and click on the "wrap quote tags" tab at the top of the reply box. Its the little yellow square icon located to the top right of centre.

There's a test forum here for all stuff like this if you want to practice a bit.

yoloc

I was chatting to my brother in law about his issue and he's going to correct it while the ground is still hard(ish). He owns a small machine and will be purchasing the extra pipe/percolation stone needed in the next few days for doing the work. Today he found out that the engineer who signed his house off now lives down under in Australia so can't really call him out to look at it.

Me and him are going to crack on at the weekend and correct this ourselves but he wanted me to upload this picture below to show what we'll be doing which give's a few day's for anyone to correct us if we're not doing it to the SR61991

He was going to contact another engineer but does't see the point in paying someone a few hundred euro's just to stand over something we know that we're doing right. If this was a whole new design for a percolation area or even moving it to another part of the site then yes, he would have hired an engineer but not for something so small work as this.


Here below where you see the red line crossed over the distribution box, we'll be moving the box inside the 20m max aloud for a run of pipe in a percolation area. We will also be connecting all the 4 pipe's with they're own run of pipe coming from the 4 holes in the distribution box rather that just T'ing off one pipe. We will also be adding 1.5m pipe to the end of the 4 run's and taking out the last run at the bottom connecting all 4 pipe's.