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Providing Water on Allotments – Rainwater Harvesting

Many allotment sites do not have the benefit of mains water. Rainwater harvesting and storage is the solution adopted by Elizabeth Way Allotments, Coventry. Many thanks to them for sending the information and photographs.

Connecting the taps to the IBC

As their allotments never had access to running water, they decided to improve the situation and construct their first water station. The water station is additional to plot holders own water collection systems, used for emergency and dry spells though the summer months.

Even sites and gardeners with access to mains water would be well to consider installing an independent supply system. Whenever we get a hot, dry summer and need to water it seems a hosepipe ban is implemented. These bans only apply to mains water not that from your own storage.

They say:

Firstly, we would like to thank the Coventry City Council & CDA&G for their help and support with this project. The construction as you can see is wonderful for the environment, completely stand alone, can be constructed in any spare area on any allotment or perhaps smallholding.

The water harvesting station provides a cost effective and a wonderful addition to any allotment. This design is easy to erect, with a cost ranging from £500.00 to £1000.00 and can be erected by members with general handyman experience.Once constructed it comes with little maintenance and gives many years of free water.

Framework and collecting roof in position.

Firstly they decided to install two strip concrete footings as their ground is unstable at certain times of the year. Next they constructed a timber frame to support the Perspex sheeting. This sloped down to a standard gutter system to supply the storage tanks below. The posts are seated in standard Drive-in Post Anchors.


I can see a potential problem with the design in high winds where the force would be upwards on the sheeting. It’s important that the sheets are properly fixed to the frame.


Storage is in four IBC containers. These standard sized – one metre cubed – containers are readily available second hand on Ebay at around £50.00. Look for “FOOD GRADE” containers to avoid any poison’s that were previously stored in the tanks possibly affecting the produce grown

Each container is able to hold 1,000 litres giving 4,000 litres when all four containers are full.

Placing the containers

The IBC containers need to be lifted from the ground to enable easy filling of watering cans etc. This is accomplished by mounting the containers on concrete blocks, three high. Use the high density blocks because they will have to carry a lot of weight. The builder’s merchant will point you to the right product. 1,000 litres of water weighs 1,000 kilograms plus the container weight.

It’s critical that the support is sturdy and stable as a collapse is potentially dangerous. Ensure the blocks are placed on a firm base. Do not use pallets to support the tanks. Over time the pallets will rot and collapse.

Connecting tanks together

Filling Watering Can

Filling Watering Cans

Hose union bib taps have been fitted to each unit, and each container has been fitted with small section of garden hose with the use of jubilee clip to cut down on the waste of water when in use. Each container is connected by the use of standard plastic waste pipe and fitting, all available from local plumbing merchants.

Keeping the water sweet

As rainwater enters the first container make sure that the hole put in top of tank to receive the water is a tight fit and sealed to avoid mosquito’s & larvae at a later date, always keep the top inspection lid in place to help avoid this problem.

It may be advisable to obtain black covers for the tanks to help with discolouration in water over time if funds allow. There are a number of inexpensive commercial products available to keep the water clear of insects, algae and bacteria such as legionella. See Keeping Water Clean & Safe

Completed Water Capture Station

Posted in Allotment Garden Diary
15 comments on “Providing Water on Allotments – Rainwater Harvesting
  1. Robert Lawrence says:

    We have done a similar project with 4 off IBC’s. They work really well, taking the supply from nearby roofs we can fill one IBC with about two days rain fall. We did not run out of water once this year. We were advised to screen the IBC’s to prevent the sunlight from turning the water green, this we did with a green tarpaulin. We also filtered the water with a 25mm mesh, then a 5mm before water entered the IBC’s this keeps the water much cleaner. We’ve kept our IBC’s separate and not linked them at the moment, but we have been offered four more IBC’s which we will use as header tanks and link them. We bought our first IBC’s on-line for as little as £25 each, but now we have found an even better supplier! (Free). I would be happy to circulate pictures of what we have done, if anyone is interested. Robert

    • John Harrison says:

      Hi Robert
      If you want to email photos across to me I will happily pop them on the site. Or, if you’re registered on the forums you can post images easily and directly.

  2. Paul Williams says:

    A great idea and looks to be quite scaleable, too.

  3. diane drinkwater says:

    Does that trigger the requirement for planning permission by having foundations?

    This document suggests it might.

    • John Harrison says:

      I really can’t see the planning authorities taking much notice of something like this. If it was a concern then laying thick slabs on the soil to spread the load would avoid that, I think.

  4. Ray Hulm says:

    Concerns about climate change and because our allotment site relies on groundwater, we decided a couple of years ago to publish a short report for members on the future of our supply. It might interest others.


  5. Robert G Rogers says:

    My Chicken Aviary has a 10 sq mt Galvanised corrugated roof that all goes into a 30 gal water Butt
    I also have 3 additional 30 Gal Butts and 2 x 22 Gal Butts off sheds and greenhouses + 2 others approx 40 gals together that are filled from chicken roof supply via a battery drill powered pump used for hand washing etc
    All materials were Salvaged or given I have bought 1 new 30 Gallon Butt only
    And all around me I see roofs with no means of collection or storage

  6. Louise Jutsum says:

    Great ideas. The webinar on this at the National Allotments Association was very good. I have been saving yoghurt cartons etc to put in 5 trays. Have filled a tank sofar this autumn.

  7. Derek says:

    It’s also a smart move to capture water because there’s no running up and down to the water supply. A cheapo eastern solar panel(with controller) a couple of knackered batteries (you don’t need to start a car with them anymore) an eastern 12v water pump (5litres a minute is cheap and it’s where I started) and you have a hose pipe system. Run some lengths down your plot, tee in with a cheap isolation tap and you have multi water points for your short hose. incorporate a wifi relay for the pump and you wont even have to go back to the pump to turn it off to change where you’re taking water from!
    With that setup and 2k litres available I didn’t run out of water (down to 200-ish litres) during the 3 weeks of hot weather even with soaker hoses in my beans and squashes trenches which were turned on for 5 minutes a day.
    The containers are in the shade, they are fed by my 6×8 shed and a 4ft square cover, there’s a debris mesh on the way in and a micro mesh filter on the way out to protect the pump and sprayer. (they are tee’d into each other so it takes from both at the same time)
    It may seam a bit over the top for an allotment but it is more than achievable by anyone and generally makes things easier all round when you can give your crops the amount of water they need without all that walking up and down to the water tubs. plus there is power available to charge your phone (all controllers have a usb port) and also provide outside light and security.

  8. David Whiting says:

    In process of building an IBC Water Harvesting System
    -I have one lucky break, at the back of my plot a very slow running stream. I’m looking at building a little catchment area within it and Reed Planting next spring It will have be done slowly so I don’t break any planning issues. Last Winter there was major flooding – and then may be a different case. So looking into solar panel to draw off as tedy amount – Will post more when completed. If I could only lay my hands on FREE IBCs

  9. Michael Armitage says:

    Great ideas!

    I found that a ‘free’ filter could be made from taking any scraps of hard plastic debris netting which had been left over from the beds, literally rolling them into a small ball, and plugging them into the down pipes!

    You could make several ‘filters’ in the pipes on the way down to the IBC, and it takes just a minute to hoik them out after the winter, when any caught-up debris has rotted.

    Because the mesh is quite cellular but robust, there is no danger of these filters actually blocking the pipes.

  10. COUANN BENNER says:

    We have been doing this for years. We do not have mains water so our wells cold go dry in a long dry summer, the watertable gets low anyway by the end of august so we got black food grade IBC tanks and placed them in areas above the orchard, garden, animal sheds and house so we could gravity feet to wherever we want. We fill them when there is a surplus of water in about March/April. It has worked very well for us. I understood Black was food grade and transparent /white is not. This is a super idea for allotments.

  11. Julia says:

    I build a roof over my 3 bay compost station and put guttering leading to the first barrel with 6 other barrels linked. It rained heavily this year and so I have 7 full barrels and have not really had to use any of it over the summer, except for the poly tunnel. I am sure it will come into its own over the next years, as we have no water on the plot and I was dragging water I have to pay for from home. Really happy to have the system in place and I would encourage all to do likewise.

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