Forum home› Fruit & veg
This Forum will close on Wednesday 27 March, 2024. Please refer to the announcement on the Discussions page for further detail.

Rainwater tank far from downpipe

AlbeAlbe Posts: 135
in Fruit & veg
I'm "designing" the irrigation system for our veg garden. Trying to maximize efficiency I want to attach the IBC 1000l water tank to the pipes of the largest roof, so the roof of the house (also available a garage, and a garden house, but they have small roof)
However, I want to store the IBC tanks, which are big and ugly, far from the house, "hidden" out of sight behind the garage, so the water hose from the house downpipe to the tank would have to be long, 25m. I understand the height argument, gravity only pulls water downward, not upward, but how about horizontal distance, will there be an issue with a long hose bringing water to a far tank?

«1

Posts

  • AlbeAlbe Posts: 135
    I am planning NOT to have a pump to feed the tank from the downpipe (of course I will use a pump to feed FROM the tank). 
    Will the distance be an issue?
  • send_to_alansend_to_alan Posts: 21
    I would intercept the downpipes using standard fittings, and run them via, standard solvent welded drain pipes to the IBC, can you run the pipes along a fence at 2m height and drop to say 1.5m, then add a return flow pipes back to the drains, so it can overflow.  Also will put in standard gate valves to switch the system and of course a couple of filters.  Maybe insulate or bury the tank to prevent freezing.
  • Lizzie27Lizzie27 Posts: 12,494
    I would have thought it would be far easier just to use the garage roof to collect the rainwater into your big tank, which would fill up in time. It is surprising just how much water comes off a small roof.
    North East Somerset - Clay soil over limestone
  • SkandiSkandi Posts: 1,723

    In an ideal world with no friction the red areas would all need to be full of water to push water into your tank. In reality there is a lot of friction inside 25m of piping and the head of water required to push through at any useful speed would require more water to be sitting in the pipes going up the house. in a 2 story house it might be possible with the extra couple of meters height. But my gut feeling is that you would waste 90% of the water as it simply couldn't pass through your piping fast enough.
    On a system like you have drawn you will also need a first flush diverter and a filter before the water enters the pipe, as any debris will accumulate in the buried pipe and soon block it.
    The red bits of pipe will always have water standing in them which will be an issue when it freezes.
    Why not bury the tank near the house? digging a 1m3 hole would be less effort in the long run that that system.

    And as lizzie says a garage roof will very soon fill an ibc an 18m2 roof only needs 5.5cm of rain to fill the tank.
  • StephenSouthwestStephenSouthwest Posts: 635
    To answer your question - no problem, water flows downhill, so as long as the input to the tank is lower than the output from the downpipe, there's no problem.
    BTW - a rule of thumb is that in the UK there's a metre of water falling a year, so a square metre of roof will produce roughly a cubic metre (1 tankful) of water a year.
  • AlbeAlbe Posts: 135
    Thanks everybody for helpful discussion.

    send_to_alan, very good suggestion. This would have the benefit of having the pipe empty (dry) when it's not raining, better for hygiene. But house and garage are disconnected, driveway is in between, no chance to run a pipe continuously and elevated along a fence. The pipe/hose must be at ground level (or lower).

    Lizzie27     said:
    just to use the garage roof to collect the rainwater into your big tank, which would fill up in time. It is surprising just how much water comes off a small roof.
    Well, I looked at data. The garage is 2.5m x 6.5m, rainfall here is 60cm/month, so from the garage ca 1.4qm/month. I have garden water data from last year (no tank last year) and lawn and tomatoes took much much more.

    @Skandi
    Yes, because of the distance and the friction the top of the pipe must be somewhat higher than the top of the tank. I can do max 1m higher. I will check this before installing and I guess this will do. I will report here how it goes...

    Yes, winter freezing is a concern (btw, minus 13C here yesterday!). I think the answer is simply I will have to remove the hose in autumn and reinstall it in spring. I will leave it sitting on the ground (not buried) for simplicity (no fun lifting up the new driveway twice every year).

    Buried tank would be best, agreed. But this would be expensive, I'm cheap. Maybe I would need a company to dig, and at least I would need a different type of tank, I can get an ICB 1000l tank delivered for like 75eur, undeground would cost at least x10 more.

    Thanks everybody x your opinions, I appreciate it.
  • StephenSouthwestStephenSouthwest Posts: 635
    edited February 2021

  • AlbeAlbe Posts: 135
    Or would it suffice if instead of removing the hose I just disconnect it at either (or both) ends? 
    In principle this should do. In practice, I wonder if it ends up freezing first one end, then freeze the other end, then when the water trapped in the middle section (at lowest ground) tries to freeze does not have space and burst the whole pipe/hose...
    overconcerned...?
  • steephillsteephill Posts: 2,841
    If you already have a pump then why not use it to do occasional transfers from water butts on the house drainpipes? That would avoid having hoses lying around on a semi-permanent basis and gives you more water storage capacity.  It also takes away any worries about dealing with overflow from the IBC.
  • Hostafan1Hostafan1 Posts: 34,889
    My gut feeling is that during a downpour the house downpipes will overflow as the water wont be able to move through the underground pipe quickly enough to cope with rainfall. 
    I might be 100% wrong though
    Devon.
Sign In or Register to comment.