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foaming rain water tank.

I catch and store water from my bungalow roof, this water goes into a very large, old and well used galvanised tank and two equally aged and very large plastic butts. I clean these out once a year. The water from these is clear and does not smell but this year when drawn into watering cans it foams why is this ?  


  • LynLyn Posts: 21,875
    I dont know why but ours always does that as well, it doesn’t seem to hurt the plants. 
    Gardening on the wild, windy west side of Dartmoor. 

  • DovefromaboveDovefromabove Posts: 83,785
    I’ve noticed this with some water butts ... it does seem to be due to water from some particular roofs ... as Lyn says it doesn’t seem to affect the plants ... but I wouldn’t use it on tiny newly germinated seedlings. 

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.

  • My plants thrive so it obviously does no harm I am just curious as to what causes it. :-)
  • TheveggardenerTheveggardener Posts: 1,057
    edited August 2019

  • wild edgeswild edges Posts: 9,342
    It might be a similar process that causes foam to form on the shores of lakes when the wind whips up the waves. It's something to do with suspended protein particles bonding together under agitation I think. Salt water fish tanks use the process to filter the water too. Or it could be soap residue I suppose. Do you have dormer windows that get cleaned?
    Tradition is just peer pressure from dead people
  • NollieNollie Posts: 7,024
    Your first explanation sounds plausible WE. The microscopic protein particles - presumably from decaying organic matter like algae, leaf litter, bits of dead insects etc., on the roof and in the gutters, get churned up by rainwater pouring into the butt.

    Unless you leave it long enough so its all starts fermenting, wouldn’t have thought it does any harm. Waterbutt Homebrew - now there’s a thought 🤢 
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • wow ! yummy no wonder the plants like it :-) As long as it doesn't pong I'm ok. Thanks
  • I don't have Dormer windows and there is no way detergent can get into the tanks your explanation sounds about right to me Thanks
  • wild edgeswild edges Posts: 9,342
    Never underestimate the tenacity of a small child with a bubble machine ;)
    Tradition is just peer pressure from dead people
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