Green Building Forum - Rainwater harvesting DIY underground.

Rainwater harvesting DIY underground.

Hairlocks — Wed, 11 Mar 2015 15:14:32 +0000

I have a fairly unique rainwater harvesting idea.

Want to install small tank underground next to my soak away (new build house) and pump the water 25m in the height and 150m in distance to our allotment field into above ground IBCs. (black 25mm MDPE pipe) and then use the water for the allotment, livestock, and gravity feed outside taps near the house (another 25mm black MDPE pipe) while I am digging the trench (digger needed for other landscaping) I will put a blue main mdpe and an armoured cable (on top) in the same trench.

The house and garage foot print is about 110m^2 in total.

The soak away is under where I want to put overflow parking (e.g. a visitors path), and have a track up to the field (350Kg tractor)

Any ideas on a suitable small underground tank and cheap powerful pump. My current tank idea is to make one with Inspection Chamber Risers (sewerage manhole) and fish tank sealant, as I think I only need 200 litres. Plus I want to make the install as cheap and easy as possible.

Do I need to worry about leaves and stuff, would it be easier/cheaper just to clean it out in the autumn.

Anyone have any better ideas?

Any pointers to a good pump and float switch?

Rainwater harvesting DIY underground.

Hairlocks — Wed, 11 Mar 2015 15:25:32 +0000

Seems like a pump with such a large head is going to be fairly restrictive.

Rainwater harvesting DIY underground.

Gotanewlife — Wed, 11 Mar 2015 15:38:44 +0000

Posted By: HairlocksSeems like a pump with such a large head is going to be fairly restrictive.

As in cost you mean?

Rainwater harvesting DIY underground.

Hairlocks — Wed, 11 Mar 2015 15:53:03 +0000

yes, a standard dirty water submersible pump (Â£50-Â£60) has a max head of about 8m but many makes available. I am going to need 30m+ (well pump about Â£300 so far, and clean water only) . I need to find an accurate way to measure it. Thinking of a water pressure meter and filling the pipe.

Rainwater harvesting DIY underground.

tony — Wed, 11 Mar 2015 16:06:58 +0000

why not catch water on or above the allotment? 200l is very little water, try to keep leaves etc out, a catch pit will do this, why waste energy pumping it up, may as well pump straight to outside tap.

Rainwater harvesting DIY underground.

Peter_in_Hungary — Wed, 11 Mar 2015 19:46:53 +0000

Hi Hairlocks
Over here you can get a submersible vibrating membrane pump that is good for about 55M lift (max 6 bar but the closer to 6 bar the less the flow) for about 35GBP - they are a bit noisy but do the job

Otherwise I have used Pentax pumps for years on my water systems and found them to V. good. (we are on borehole water) They are surface pumps with a max suction of 6M and max hight depending on model e.g PM80 (about 65 GBP Nett here) has a max lift of 61M or PM45 (about 45 GBP Nett here) has a max lift of 35M. They are not self priming so a good non return valve is needed (or mount the pump below the tank which is what I do) I have no connection to pentax other than a happy user.

A quick search on google showed http://www.allpumpsdirect.co.uk/Speroni-KPM80-Volumetric-Pump - different name but looks identical to my pumps.

I would agree with Tony 200l. is not much water, in fact IMO 200l would not be worth the trouble as this amount would be very quickly used for the usage you describe (water for the allotment, livestock, and gravity feed outside taps near the house) Using an IBC or 2 would make more sense to me!

Rainwater harvesting DIY underground.

Hairlocks — Thu, 12 Mar 2015 08:32:51 +0000

The allotment is the maximum height of may land, and only has a little shed as a collection 6ft v 6ft.
I plan to put several IBC's on the allotment to store it. as use most of it on the allotment.

The idea of only 200l next to the garage is because I can't see why it needs to be bigger there at extra expense (and I am not sure I have the space), when most of the water use will be on the allotment / fields.

I would like electric up at the allotment and main water up on the allotment anyway, so was really thinking of a way to use all the rainwater going into the soakaway.

I will go and do some sums to see the running cost of the idea and installation.

Thanks for the pump link

Rainwater harvesting DIY underground.

Hairlocks — Thu, 12 Mar 2015 09:20:45 +0000

Probably not clear enough. I would have several IBCs on the allotment where the water is used from and stored. The 200l tank underground next to the garage would be just to provide a collection point to feed the pump to get the water too the allotment. Also provide a sensible buffer to stop the pump rapidly switch on and off.

Rainwater harvesting DIY underground.

dathi — Thu, 12 Mar 2015 13:14:10 +0000

i buried an ibc for my collection tank . I dug the hole slightly larger than the ibc poured concrete into the base and dropped the ibc with its cage in. then filled it up with water and filled hole with concrete . you can get lots of tank fittings on ebay if you look for koi pond fittings.

Rainwater harvesting DIY underground.

haplessDiyer — Thu, 12 Mar 2015 14:36:39 +0000

would a manual pump work, savig energy? Shouldn't take long to pump 200 litres every time it rains?

Rainwater harvesting DIY underground.

CWatters — Thu, 12 Mar 2015 19:22:45 +0000

We pump our rainwater about 150m horizontally using a 4 reels of hose because the allotment is the other side of a road and the village green! Takes about 3 hours to fill our 1000L IBC so the flow rate flow rate we get down the hose is around 5L/min.

Going up 25m you will loose at least 2.5bar in pressure so I think I'd be looking for a pump that can deliver a decent flow rate at say 4-5bar.

Perhaps look at the Stuart Turner Diver 35 or 45 series of pumps around Â£140 online. Their data suggests the 45 can manage a 40m head although I haven't checked if they can pump dirty water.

http://www.stuart-turner.co.uk/products/stuart/submersible/diver-45/
Â£130..
http://www.fountaindirect.co.uk/stuart-turner-diver-45.html?gclid=CO-kjZ_Eo8QCFQXmwgodNyUADg

Despite having a reasonable filter our rainwater tank has acquired a layer of silt in the bottom. If you go for a submersible pump I would raise it off the bottom of the tank at least 6" and allow for some loss of capacity.

Rainwater harvesting DIY underground.

Triassic — Thu, 12 Mar 2015 21:52:29 +0000

Posted By: Hairlocks

Any pointers to a good pump and float switch?

Not sure where you are located but you can pick a pump cheap at auction. Search for Bidspotters and search for 'pump' on there auction site, they have loads.

Rainwater harvesting DIY underground.

ringi — Thu, 12 Mar 2015 22:08:44 +0000

Can you put a IBC half way up, and then do the pumping in two goes?

Rainwater harvesting DIY underground.

Hairlocks — Fri, 13 Mar 2015 10:40:03 +0000

All good stuff,

dathi, I am considering a IBC now, as the heavy rain fall could give me more than the 200 litres, I found a 350 l underground tank for 200, but I guess it still needs concreting in. Any idea how much concrete I need with the IBC, I take in mixing it myself in a small mixure is going to take a long time and it would be cheaper to get a delivery

happlessdiyer; now a manual pump may be feasible, going to try a build on of these to try it out https://www.youtube.com/watch?v=vaho7JSVS1I . He tested the diy check values to 50psi. It will give the wife some exercise while it is raining (installation in garage so could be changed later if needed)

CWaters; I bought a water pressure meter yesterday and I only have 3.6 bar at the house ground floor (next to stopcock, with no water being used). I this is low enough to wonder whether mains water will get up the hill (25mm will help a lot in this case). Going to have to measure the height of the hill, as the 25m is an estimate from an OS map. I was going to have the bottom few inches of the tank I use for silt and gunk to collect in.

Have you thought about 19mm (3/4") hose pipe for your needs, you could probably increase the 5l/min to 12.5l/min. (if you need it)

Ringi; a IBC half way up would be a backup plan. The water mains may need a pump half way up the hill as well.

Rainwater harvesting DIY underground.

SteamyTea — Fri, 13 Mar 2015 11:08:10 +0000

Posted By: HairlocksI only have 3.6 bar at the house ground floor

Won't that mean you will get 2.1 bar at 25m height?

Rainwater harvesting DIY underground.

Ed Davies — Fri, 13 Mar 2015 11:53:36 +0000

Isn't it 1 bar is 10 metres so 25m is 2.5 bar so take that off 3.6 leaves 1.1 bar, less pipe friction losses?

Rainwater harvesting DIY underground.

SteamyTea — Fri, 13 Mar 2015 11:56:33 +0000

Fat Fingers on my behalf. Yes 1.1 Bar.

I must find out how to get my laptop to book with the number lock on to save me using the numbers above the letters.

Rainwater harvesting DIY underground.

Hairlocks — Fri, 13 Mar 2015 12:39:00 +0000

I will get 1.1 bar at 25m but it could be 35m high, and then I would only get 0.1 bar which I can't see being usable. Going to buy several hoses to measure the pressure with.

Pipe friction loses are quite high as well at the distance I am talking about.

Rainwater harvesting DIY underground.

Hairlocks — Fri, 13 Mar 2015 14:55:53 +0000

If it is 1.1 bar left for the pipe, I will get 0.34 m3/h out of a 1/2" hose, 5.6 l/min (well at least water leaks would be slow.)

With 25mm pipe I will get about 1.9 m3/h or 31.6 l/min. so definitely burying a proper pipe, assuming it is not too high.

Rainwater harvesting DIY underground.

dathi — Tue, 17 Mar 2015 18:23:59 +0000

Posted By: HairlocksAll good stuff,

dathi, I am considering a IBC now, as the heavy rain fall could give me more than the 200 litres, I found a 350 l underground tank for 200, but I guess it still needs concreting in. Any idea how much concrete I need with the IBC, I take in mixing it myself in a small mixure is going to take a long time and it would be cheaper to get a delivery
.

i just used a belle mixer and wheel barrow only put 4" around the sides and base don't forget to put an overflow into the tank and drain it to somewhere suitable

Rainwater harvesting DIY underground.

Hairlocks — Thu, 26 Mar 2015 11:08:36 +0000

I did some measuring in the end, and developed my ideas.

Pressure near the top of the field turned out to be 2.0 bar so actually only a 16 meter raise. I did measure the water pressure in the hose at the house after disconnecting it from the mains (blocking it with the water pressure meter) this indicated only 0.4 bar which must be wrong, house is almost 9 metres high and I am above it before I lose sight of the house. Going to look for pumps again with new information.

Probably give the DIY mixed concrete a go, only need about 1m3. Was going to drain it back to the soak away the builder put it.

I may even use the rainwater for the toilet (worked out a way to connect them up ) and for the washing machine (seems to be on everyday with kids)