Oxbow16

That's interesting and might explain why the views on it are so different. I see that it is used on the side of roads, railway embankments, and places like that. Actually, I think our driveway is limestone and that seems fine. I can't imagine all the farmers across Wales and other areas who use limestone have ended up with solid land drains... Good thinking. Don't know why but it hadn't crossed my mind to go direct. I guess I imagined they didn't sell to end users and only to the middlemen who sell it on, like with so many other things in the building trade and beyond. The one problem might be access. We are on a narrow(ish) country lane and I'm not sure they'd have enough swing to be able to back into our driveway. If you get a moment and are happy to, would be handy to hear of any recommended suppliers in the area. I'm pleased to hear that's what the locals use and gives me more confidence to use it myself after reading all of the "avoid it" advice. Thanks everyone for all the help.

Hi Miek Can you recommend any suppliers? I'm in Carmthenshire too... Yes, I presumed that's what everyone must be using as that seems to be all you can get locally. Which also makes me think it must be suitable. But then why are so many people saying to avoid limestone I wonder??? Confusing. Thanks for your reply

@Temp - that's both interesting and worrying to hear, not least of all as it seems that's all that's available locally. Strange question perhaps, but you don't have any photos of the problem you had and/or the limestone used by any chance? @PeterW - The cheapest guy is the same price loose or bagged. Maybe because he is just a few miles away?? Next cheapest was loose. Another loose delivery quoted over £50 p/ton!

Thanks for all the replies. Well, I guess I need to call more and perhaps call further afield. I thought delivery would be the crippler, so I kept to local. AND it's good to support local business. But of the four I called, £37 inclusive was the cheapest. Hmmm...

A metre is the maximum depth to test for this... I presume you mean a metre to the bottom of the 300mm test hole? Or were you referring just to the main test hole? So in terms of the failure, how bad was it? Did it take days to drain? Weeks? Still full now? I did read lots about "clay caps" and far more permeable soils beneath them. The trouble is that for wastewater the pipe can be no lower than 700mm...

How chronic was the perc test failure? And how deep was your 300mm hole when you did the test?? Are you discharging from a septic tank or sewage treatment plant? Ta

Hi I came across septic tank filters recently and will be getting one for my tank. It sits in the vertical part of the outlet T pipe and helps keep any remaining suspended solids out of the drainage field. Apparently they are widely used in a lot of the rest of the world, but not in the UK. I wondered why? They're cheap and seemingly effective, so I'm puzzled as to why they're not installed as standard. It seems many people haven't even heard of them, and a lot of the large drainage companies don't even sell them. Is anyone here using one? Any thoughts as to why they're not common? Cheers

I thought that was the Joy Division "Unknown Pleasures" album cover for a moment there!

I'm glad the thread was resurrected... ...because now the wife won't be!! With a hole like that they'll never find her!

The finished article: Drainage Field Gradient Calcs with Graph.xls

What I did was quite crude tbh, and not particularly accurate either I'm sure. But close enough for now. I used string and started it just above ground level then put in two stakes along the length of land. I attached the string to them, keeping it as tight as possible. I'm guessing there must have been a little bit of bow to the string, but none that I could see when looking down the line so nothing major. I used a spirit level to level the string, and then a tape measure to measure then height at the various points....

No, I'm afraid not. But I think I've got it... Adding a minus to each height figure in the excel sheet does what I'm after... Got there in the end thanks to you guys

It varies... There are no straight lines here!

Yes!!! Well, almost.... You'll have to forgive me if I gave the data wrong, or gave it in the wrong way It's been a very long day and my mind's a bit frazzled! The land slopes downhill, so the graph is correct other than that it should start high and end low... Is that possible? Sorry for all the confusion and thanks for the great help.

What can I say... WOW! Many thanks I'm well impressed. I only wish I had the data to do any of the above justice! I don't though unfortunately. All I have is length and height, so I was thinking more of a 2D plot of the data.... I'm more than happy to share the figures if anyone can do anything with them. I have to admit though that - having never done anything like this before - I really was just making it up as I went along. In hindsight, I should have measured at regular intervals rather than the random intervals I chose. But the reason was because the land is very unimproved grassland and so I avoided measuring height where there were big grassy clumps or other irregularities underfoot. So here are those figures: Distance CM Height CM 140 15 330 30 510 39 750 45 1280 60 1520 60 1790 85 2020 97 2270 110 2530 125 2660 129 2820 132 2930 137 3130 137 3370 141 3650 137 3960 138 4000 145 4120 149 4290 147 4510 142 Huge thanks

Thanks dnb... I'll reserve judgement on the weird bit until I understand what you mean If you're able to explain that in a more dumbed down step by step I'd massively appreciate it. I have excel. In fact, I use it so often that I have been known as Maxcel in the past! But a lot of its features I'm completely ignorant on. Cheers Max (cel)

Hi all I've been out in the garden today measuring the undulating lay of some of the land. It all slopes gently downhill, but to varying degrees in different places. I have measured at different points and now have a bunch of "at this distance, the ground is this height" figures. It would be really helpful to visualise this and I wondered if there is some kind of on line "app" or similar which will allow me to punch in these figures and produce a visual representation of them. Anyone have any ideas? Many thanks

Hi. I don't know much about such things so please add the required salt to my comments Two things I have learnt whilst investigating my land for a suitable drainage field (albeit for a septic tank) are: - The land was very different in different areas. My first hole never drained which led me to think it was clay and impermeable. Turns out though that it is likely the land in that area has had human intervention of some sort, as when - by chance - I did a second hole in a different and more out of the way spot, it percolated very well. Obviously this might be irrelevant if your plot is on the smaller side. - When I was reading up on the subject I came across several people talking of a "clay cap". And that if there is one, getting passed that may mean reaching more permeable ground conditions. I didn't pursue this myself because the other hole worked so well so there was no need. And I was digging by hand and so couldn't go too deep. Perhaps if you've had a drainage engineer involved this has already been thought of and/or deemed irrelevant. But it was a couple of things I came across whilst being faced with poorly draining soil and so thought there's no harm in sharing. Good luck!

Crikey, that's a lot of water! This is in Kent? Shocking and a shame to hear. That being said, it seems the water companies pretty much have a free license to discharge raw sewage to watercourses. So I guess they're just cutting out the middleman in a way! PS - I guess the water does look quite brown in that photo

Seems ever since the 2020 new rules RE septic tanks discharging to streams (no longer being allowed), septic tanks have gotten a bad rep. Certainly here in Wales - and I think in Scotland too - a septic tank with drainage field is preferred by the powers-that-be over a sewage treatment plant with discharge to stream. This thread isn't the first in which I've read people asking whether septic tanks are even still legal. A properly functioning tank discharging into a properly functioning/installed drainage field is no bad thing! Bet that was fun for the driver on those roads!

What was the total depth of the hole you dug? The 300mm cube you fill and test should be below the bottom of the proposed outlet pipe depth. So if the drainage pipe itself will be 300mm deep, you fist dig a 300mm deep hole (width is irrelevant), and then AT THAT LEVEL you dig the 300mx300mx300mm test hole. Fill that hole and allow it to drain overnight. Then refill to 300mm the next day and time how long it takes to drop from 225mm to 75mm, which it sounds like you did. You should refill a further two times and time these in the same way. Then calculate an average. Hope that all makes sense! You then put the figures through an equation, which I can find for you if you are interested? Let me know. I would personally try another hole in another area. If there's any chance the area you tried the test hole in has previously been compacted, this may have an impact. I say all of this because it is exactly what happened to me recently. The first hole chronically failed. I ruled out a drainage field based on that, but then decided to try an other hole in another part of the land, and that had great results. If you went for a Sewage Treatment Plant, where would you be discharging to? A stream?

@BotusBuild Curios as to what you decided in the end?

What I can add is that I spoke to a few suppliers about it and their answers varied as to why black corrugated cannot be used. For example: - Because if there is a problem with the tank and more solids were getting through to the drainage field, the pipe would clog more easily. - Smooth pipe is better for even distribution across the whole drainage field. It ensures a smooth flow. - You can use black corrugated land drainage pipe. But you should also follow building reg (!).

Hi there I don't have an answer for you, well - at least not a full one. But it is a very good question and one I have been looking into as well. What I do know is that the black corrugated stuff in your second link is against building regs. It even says so on the product page: "Not suitable as a dispersal drain for septic tanks". Note also that the second link stuff says it is single wall, not twin. Why this is the case I'm not sure. I can see that the black corrugated isn't kite marked. And maybe that's all there is to it? If there's more to it, then I would love to know why it is not considered suitable. In terms of durability, I cannot see it being a problem seeing as this is what farmers use as land drainage. A farmer's field sees a lot more "action" than the average garden! So if anyone knows of other reasons why it isn't suitable, please enlighten us both :) Cheers