Comments Please on Rainwater System Idea

[crispy]

Hi there,

I'm planning a homebrew rainwater harvesting system to supply water for the vege garden and for flushing toilets. It will be based around 2 black IBCs stacked in the garage. I'd like to hear your thoughts and ideas for improvements about my initial plan for the system.

We have approx 27m2 of roof over the garage, drained through one downpipe at the rear of the garage, and approx 42m2 of roof over the house, drained through two downpipes at the rear of the house. I want to harvest all of this. We have another 18m2 of roof that drains to the front of the house that is too difficult to harvest.

My idea is to buy 3 "3P" water butt filters and install one on each downpipe about 1.3m above ground level. Then feed the water into 40mm waste pipe welded with evaweld. The waste pipe will run down to the ground and then 6" underground alongside the garage. At the point outside the garage just adjacent to the IBCs the waste pipe will come up above the ground to a height of 1.2m, turn a 90" bend and go through the garage wall. It will go directly into the main IBC at this point, through a hole that I cut in the side near the top.

I'll need to deliver the water to two WCs in the house, one ground floor and one first floor, and to a garden tap installed in the wall of the garage just outside the IBCs. I'll do this with a 12v pump with 8m head mounted on the floor of the garage just next to the IBCs. The pump will take water from the bottom tap of the main IBC and supply water via 10mm PVC pipe to a header tank and then down from there two the two WCs. I'll series wire a float switch in the IBC and in the header tank to control the pump.

The second IBC will be stacked on top of the first and water will be pumped into it from time to time by opening a tap and manually running the 12v pump. When the main IBC empties it can be refilled from the top IBC by opening a tap.

How does this all sound?

There are a couple of odd bits that I'll explain. This system appeals to me partly because of the supply of emergency water it offers. Hence the 12v pump which I can use in a power cut from a battery. In an emergency we would treat the water with bleach and course filtration and it could be used to drink.

The header tank is a pain because it means I need to run a flow and return pipe up to the loft which means spoiling decoration in a bedroom. I would much prefer direct connection from IBC to WCs via a pressure pump and will investigate this.

I don't know if I have enough filtration - its limited to the coarse filter on the 3P filter collector. I also don't know if the idea of running waste pipe from the 3P filter collector will work - I prefer this idea of gravity feed into the IBC for simplicity sake but don't know if it will work in practice.

Any suggestions, comments, flames, welcome!

Thanks :-)

[desperate]

Hi crispy

I reckon you will need some rodding eyes for the underground 40mm waste pipe, I would try to go downhill from the 3ps to your storage tanks.

good luck

Desperate

[crispy]

Thanks Desperate, good idea on the rodding points.

I've found two pressure activated pumps that I think would remove the need for a header tank. Here's one, an ebay 'booster pump with accumulator', and here's another, a 12V shurflo pump. I guess the question is how fast will these fill up my 1st floor toilet cistern (10ft head with 30ft run).

[crispy]

Here's a picture of the layout. Some more thoughts:

I'm keeping the garage roof water into the upper IBC because the garage roof is corrogated asbestos. I'll use the upper IBC to feed a garden tap, hopefully the 4ft head will be enough to get a gentle stream out of a hose for watering the vegetables. If there is an emergency I'd rather use the non-asbestos water first (although I imagine if filtered through a 1 micron filter there wouldn't be a problem).

The toilets will be completely off grid - no mains backup. I think we will learn to conserve water that way. If needed I can top up one of the IBCs from a garden hose. In the future I could set this mains topup automatically but I think I'd prefer not to for now.

I'm hoping the static head in the welded waste pipe will be enough to get the water up into the IBCs, but really am not sure. Will the pipe clog up? Should I be using flexible 20mm hose instead? Perhaps this is an area for experimentation.

My only filtration is the 3P filter collectors. Should I have more pre-storage filtration? Should I have a filter between the IBC and the pump?

[dhaslam]

If you take the water inlet from higher up on the drainpipes it will go uphill itself to the upper tank.     I have just bought a bunch of these http://www.shopwiki.co.uk/_Rain+Diverter  that are easy to fit.   on square downpipes.   I am using them to fill a series of ponds, the first one is supposed to be filling,   but it hasn't rained since.

[petertc]

Crispy,

Cant see to much of an issue with this, i have something similar

http://www.navitron.org.uk/forum/index.php/topic,4588.0.html

I have used black mdpe 32 mm  water pipe as my method of getting the water to the tank.

It's best to have filtration before the pipe. I had to pressurise the mdpe pipe this spring to clear it out.

I have one of these filtters fitted on my tank http://www.organiccatalogue.com/catalog/product_info.php?products_id=2596&osCsid=1ba7d2f66a7cf8ddbed963d3d4a02333but  but they are meant to go onto the gutter down pipe it does a good job .

i also have filtration on the outlet of the pump this is from screwfix. I would advise a small pressure vessel as as the toilet cisterns fill up the pump will cut out on pressure before the cistern is full then cut in again it's quite rapid hammering. Also fit low pressure outlet to the ball valve, may already be some on the float arm.

I have 2 jabsco pumps one in the hose the other in the garage.

You don't say what you are going to charge the battery with  i have about 60 watts of panels for mine this winter was a bit touch and go as i had to charge the battery a couple of times. i have now moved the solar panels to a SSW facing position rather than N facing! Hoping that this will be better next year. mine also runs the washing machine as well.

[crispy]

PeterC,

Thanks for your comments, that's very helpful.

Why do you need two jabsco pumps? Do you find that they are powerful enough to get the water up into a 1st floor toilet? Have you measured the current draw of the jabsco pump in 'standby' mode?

Also, how do you get the water from the downpipes into the 32mm MDPE pipe?

I'm toying with the idea of solar charging the battery but might just trickle charge it from the mains for the time being until I can afford a solar panel.

Cheers, Crispy

[petertc]

one pump is in the garage and take the water from 2 water buts this was put in first as i got fed up with the watering can !
the other pump is purely for the house rain water harvesting. so it's 2 completely different systems.
to get the water into the mdpe pipes we just have the standard water but take offs.

http://www.screwfix.com/search.do;jsessionid=GBTTXQKWRX11CCSTHZOCFFQ?_dyncharset=UTF-8&fh_search=27866&searchbutton.x=0&searchbutton.y=0&searchbutton=submit

hope this helps

PeterC

[Billy]

I use a Jabsco and a Shurflo on pressure switches.  I just checked cause you made me panic when you said how much do they draw on standby, answer = nothing thank God.  Had me worried there.   

[crispy]

Fantastic, I don't know why I imagined there might be a standby current draw, it's really good to know there isn't 

[solar_cambridge]

Avoid your idea of running the pipes underground and then raising up into the tanks. There could be water sitting in the pipes for days without rain causing it to stagnate. This is then passed directly into the tanks on the next rainfall. The water in the pipe *could* be a breeding ground for legionella.  I wouldn't risk it. Can't you get a different way of feeding the IBC's by gravity so pipes are completely empty after rainfall.

[crispy]

Avoid your idea of running the pipes underground and then raising up into the tanks.

What a nuisance  . Yes, you're right, the stagnant water might be a problem. The problem is, I need to move the water from the 7' high gutter on the extension part of the house into the next building, and with a walkway between the two its impossible to get a smooth gradient down to the tank. But it might *just* be possible to keep the water up at 7' high over the walkway. This means clumsy ugly pipework.

I guess the only other alternative is taking the water down to ground level and collecting it into a sunken bucket, then running a bilge pump from the bucket up into the IBCs. But even this is going to leave stagnant water in the pipe between the bilge pump and the IBCs.

Thanks for the advice, I'll get my thinking cap on again  

[stephend]

What's the difference between the water stagnating in the pipes vs. stagnating in the IBCs?  Is the risk of legionella really worth worrying about seeing as though you have to inhale droplets of tainted water to be infected?

[petertc]

just a correction on the pipe size it was 25 mm mdpe 3/4 id not 32 mm as i said before

[JMALW]

Hi
I have been using a system you may like to try and I don't see why it would not work with roof rainwater harvesting.

I have two IBCs to collect the water ( in my case it's from a ground water well) the water is then gravity fed to a slow sand filter suitably equipped with a ball valve to keep the level above the sand. The water is the trickled into a 7 cmtr tank built from concrete rings and sealed with epoxy resin. The water is always moving and stays aerated all the way into the tank.  I use it to flush toilets and washing machine in a 4 bed house also irrigate my lawns and garden in summer. I test it regularly for purity and it has no sign of stagnation it looks crystel clear. In the tank I put in as much copper as I can get hold of since it has a sanitising effect on microbes. The system is powered via a 5bar submersable pump with a pressure sensor to operate when a tap is turned on.
This has been in operation for 9 months and the water bills are exactly half what we used before. There is a small increase in power consumption but my calculations are  as follows: To pump 3,000 lts 1hr = 12p  (1.1Kw) plus lift pump from well = 6p (.5kw) To use 3000lts of Utility water = £7.50. Bearing in mind I used about 50,000 lts of water on watering my lawn, greenhouse and plants over a quarter You can see what savings I have made. In addition the water powers my digester gas into a 6 cmtr gasometer. Quite honestly I would never make it work if I depended on rainwater.  This year we had spells of over 6weeks without rain and that simply is not enough.

Hope this helps
PS I'm advised that water starts to stagnate if bugs, or vegetation contaminates the stored water - I filter these out with the sand filter - smuchdeke
principle.