Greenfilter Soakawa...
 
Notifications
Clear all

Greenfilter Soakaway on slope?

6 Posts
4 Users
0 Likes
316 Views
(@sparksb)
New Member
Joined: 7 months ago
Posts: 2
Topic starter  

Can I run the greenfilter soakaway pipes downhill at a 10-15% slope?  If so, what design changes might be needed?  My understanding is that typically the soakaway piping runs on a level contour, but it could be so much more useful if I could run it down the slope to water a hedgerow/windbreak.


   
Quote
Topic Tags
(@admin)
Eminent Member Admin
Joined: 7 years ago
Posts: 44
 

You need minimum drain slope (at least) to run outflow to the soakaway but I see no reason why you can't pipe down a 10-15° slope. It's not as if the water has to carry any solids. I have much steeper slopes to mulch pit tree irrigation systems on a couple of my tanks as they're on 35-45° slopes. So far, no problems with that.


   
ReplyQuote
(@kimichip)
Active Member
Joined: 3 years ago
Posts: 11
 

This sounds like a question about the soakaway itself rather than the piping to the soakaway? Are you thinking you would run perforated pipe down the hill?

If the soakaway itself is on that steep of a slope, I would be concerned about some of the water running right past the intended drip holes and pooling at the bottom...?

Is the hedgerow itself running along the incline rather than across on contour?

If I had that situation I would try to wye-off at intervals along the steeper slope into mulch pits within the hedgerow or perforated lines on contour through the hedgerow. My 10 degree pitched pipe would not be perforated. I would test the wyes before gluing to make sure an appropriate amount of water takes the turn.

Mind you I am building my first system and am not speaking from experience running the system! 

We referenced the greywater oasis site a lot for our piping design, with the caveat that our water should be clearer than greywater so we ignored those precautions (e.g. we did use some perforated pipe). We tested every branch before gluing for even distribution, and at each outlet we split for perforated pipe one way and mulch pit the other way in case one worked much better than the other.

Hope that helps!


   
ReplyQuote
(@sparksb)
New Member
Joined: 7 months ago
Posts: 2
Topic starter  

Thank you Wendy and Kimichip for your timely replies!  I'm trying to water (evenly) a hedgerow that would go down the incline, as long of a hedgerow as I can get.  I plan to use a pump to raise the effluent to the topsoil zone.  After re-reading this website I can tell that I still had in my mind that the greenfilter perforated piping was propped up on bricks as described in Anna Edey's book.  As the mulch decomposes I'd think that would create a bit of an air gap below the pipe, mitigating the risk of roots clogging the pipe.  My concern was that with pumping I'd have the risk of effluent pooling / surfacing at the bottom of the sloped trench either due to skipping over the perforations or running down the eventual gap below the perforated piping that was propped up on bricks, perhaps moving the mulch.  I can see now that the current design instead wraps the perforated piping in horticultural fleece to mitigate the risk of roots clogging the pipes and uses no bricks to prop up the piping.

Wendy, does your perforated piping run down the 35-45° hill, or do you have the greenfilters on a level terrace?

Even slowing the effluent after the pump, at the distance I'm trying to go (100-150ft), unless a perforated pipe down the incline could work, it seems like even distribution of the effluent gets too complex and costly real quick.  The only other option I can think of is to send the slowed effluent into the top of a sloped trench lined with loose gravel to slow the effluent enough (like a gabion) so it has time to absorb along as much of the trench as possible.  You'd have to make the trench conservatively long though.  At the same time maybe there would be a risk of the effluent actually being distributed over a shorter distance over time as increased organic matter improves infiltration capability.

I live in a semi-arid, windy, high elevation grassland environment with rolling hills, gully's, and soil that is 50% sand and 50% silt.  Currently rain mostly just sinks or gets evaporated, but can run off during a heavy downpour.  If I could get a long down slope planting to work it would be nice to try planting trees down the gully's to stabilize them and help temper the land by slowing the wind.  Any insights you might have into how to effectively sub irrigate a hedgerow going down a slope would be appreciated.

This post was modified 7 months ago by SparksB

   
ReplyQuote
(@kimichip)
Active Member
Joined: 3 years ago
Posts: 11
 

Hi Sparks,

If you have not yet, I *strongly* recommend you get Brad Lancaster's first 2 volumes of Harvesting Rainwater (for Drylands and Beyond). It is all about land restoration using water's natural tendencies. Your situation sounds suited to his berms & basins. You could pipe your effluent to those mulch basins using branched drains.

Your plan (running water straight down a slope) sounds more likely to create a gully rather than remediate one. If you want trees planted on a slope by a gully to thrive, you will need to slow the water so it doesn't erode the dirt from around their roots before they are well established. The berms and basins is for planting on a slope with a level basin for each tree to catch and slow the water, and a controlled overflow out of the basin, caught by the next downhill tree's basin. Sounds perfect for your situation with trees or shrubs down a slope. 

Other techniques to remediate your gullies would be one-rock dams, Zuni bowls, or diversion swales from the gully to on-contour swales.

Our land sounds somewhat similar to yours (hilly, high and dry, sandy loam, gullies). We put our trench on contour to hold the water. We don't think we will have much wastewater... we're required to put in a 44-foot trench and I'm not sure we will have enough water to serve full planting so might put in lower water plants. Greywater Oasis has good tools for estimating water use and appropriate plantings. Just another thing to consider.

Maybe I am overthinking... 10% slope is only 5 degrees, or 1" in 12... but still, if it is enough to form gullies these structures would be useful. In any case, it should be easy to put in swales and basins for that gentle slope.

All best,

Kimi


   
ReplyQuote
(@admin)
Eminent Member Admin
Joined: 7 years ago
Posts: 44
 

My advice would be don't overthink or overengineer this thing! You have a natural ecosystem in an unnatural containment situation (the IBC tank) but as soon as the cleaned water exits the tank, then I try to mimic natural systems as closely as possible. Brad Lancaster is good, yes, and I'd also recommend Art Ludwig of Oasis Design.

Also, you're not talking about a large volume of water. Just water that flushes a toilet.

I abandoned the perforated pipe distribution network after wildfires burnt out the farm here (fire doesn't play nice with plastic ...) and went for a much simpler outfall straight into a mulch pit/trench. It works fine. So in answer to your question about how I deal with the outflow on a 35-45° slope, then I pipe the water (in solid pipe) down the steeper sections of slope to the mulch pit(s) where it has depth to soak in, following the permaculture maxim with respect to water - slow it, spread it, sink it.


   
ReplyQuote
Share: