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  1. #1

    Rainwater for pond top up.

    Im getting to the final stages of planning my new pond with the overall landscaping project starting next week. All along I had in mind a water storage tank in my filter shed fed by a dechlorinating filter. The tank would feed a top up cistern at pond level (and I thought maybe a sink in the shed might be useful).

    Then I got thinking that maybe I could harvest rain water from my new shed roof and store it in a water butt in the shed and use that to feed the top up tank. This would mean I don't need to get a water feed to my shed which would save a lot of time and cost. I am not on a meter so not too worried about the water usage but still good to conserve water right?

    Is it a good idea to use rainwater from a felt roof to top up a koi pond or am I asking for trouble?

    Cheers



  2. #2
    Hi,
    I made the mistake of thinking I could top up with rainwater but found out later after reading a post on this forum that it’s not a good idea, as rainwater is very acidic and can play havoc with your ph levels. Plus it doesn’t contain the same mineral content as tap water.
    I now have to run tap water on a hose down the length of the garden to top up. I would recommend biting the bullet now to get a tap water feed in close proximity to your filters.
    Also, I would recommend getting a connection to your sewer drain with the option to feed filter waste to either the drain or onto the garden in the summer. I relied on a soak away and it struggles to cope in the wet winter months with the waste from my pond filter and the water run off from my garage roof.
    Cheers
    Ady


    Sent from my iPhone using Tapatalk

  3. #3
    I always advise against directly adding rainwater that has been collected from a roof unless it has been treated to make it safe. Bird droppings frequently contain aeromonas and other pathogenic bacteria. There also is a possibility that it will contain intestinal parasites which can infect fish. Rainwater will have a zero or near zero KH which will cause it to have a pH which is usually below 7 and can be as low as about 5.5 so it must be sterilised and some KH added before use.

    Personally, I think what must be done to make harvested rainwater safe to add to a pond is far too much trouble to go to for what it would save on the water bill but, if anyone wants to harvest rainwater, this is the absolute minimum that should be done and the simplest way to do it.
    1. Filter out suspended particles. I would allow it to run from the roof downpipe through a paper cartridge filter as used in spa bath (Jacuzzi).

    2. Add a steriliser. I would use ordinary household bleach to bring the chlorine level up to at least 10 mg/L for at least 24 hours. Potassium peroxide could be used but it wouldn't be my choice because it's messy and would be expensive for that level of sterilisation. Also, an ORP meter should be used to verify that 700 mV is achieved and held for 24 hours.

    3. Neutralise the steriliser. In either case, sodium thiosulphate would be suitable. For chlorine/bleach, the DPD4 method I put on my website would verify that there is no trace level of chlorine left. If potassium permanganate was used, check that the ORP has fallen below about 350 mV.

    4. Aerate and add sufficient sodium bicarbonate to bring the KH up to your preferred value. The recommended value for an easy life is 5°KH to 7°KH but those who are prepared to monitor their KH and pH more often can use a lower value of KH if they wish.

    After that, the water will be sterile and have a suitable KH/pH so it could be used straight away. A link to the correct DPD4 method that will verify that any chlorine or bleach that was used to sterilise the water has been fully removed is on my website here:
    http://www.mankysanke.co.uk/html/questions_answered.html

  4. Thanks RS2OOO, Grommett, bicolormoth, MustBeSomethingInTheWater Thanked / Liked this Post
  5. #4
    Senior Member Rank = Gosai KevT's Avatar
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    My friend went on holiday and next door had their roof repaired - shared gutters - cement went into gutters and then into his pond - came back from holiday - fish very sick - no idea why - went to his local koi centre with water samples 1st thing they said was is anyone building an extension? They said it happens a lot where builders are working in windy weather and the concrete / cement gets blown into a pond. He managed to sort it with water changes and bicarb / oyster shells to balance the PH out. It was off the scale and he was lucky not to get a full pond kill.

    KevT

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  7. #5
    Lol my girlfriend has strictly been told not to feed the plants near the pond with water butt water purely based on what manky said about bird droppings!


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  8. Thanks Manky Sanke Thanked / Liked this Post
  9. #6
    Quote Originally Posted by Manky Sanke View Post
    I always advise against directly adding rainwater that has been collected from a roof unless it has been treated to make it safe. Bird droppings frequently contain aeromonas and other pathogenic bacteria. There also is a possibility that it will contain intestinal parasites which can infect fish. Rainwater will have a zero or near zero KH which will cause it to have a pH which is usually below 7 and can be as low as about 5.5 so it must be sterilised and some KH added before use.

    Personally, I think what must be done to make harvested rainwater safe to add to a pond is far too much trouble to go to for what it would save on the water bill but, if anyone wants to harvest rainwater, this is the absolute minimum that should be done and the simplest way to do it.
    1. Filter out suspended particles. I would allow it to run from the roof downpipe through a paper cartridge filter as used in spa bath (Jacuzzi).

    2. Add a steriliser. I would use ordinary household bleach to bring the chlorine level up to at least 10 mg/L for at least 24 hours. Potassium peroxide could be used but it wouldn't be my choice because it's messy and would be expensive for that level of sterilisation. Also, an ORP meter should be used to verify that 700 mV is achieved and held for 24 hours.

    3. Neutralise the steriliser. In either case, sodium thiosulphate would be suitable. For chlorine/bleach, the DPD4 method I put on my website would verify that there is no trace level of chlorine left. If potassium permanganate was used, check that the ORP has fallen below about 350 mV.

    4. Aerate and add sufficient sodium bicarbonate to bring the KH up to your preferred value. The recommended value for an easy life is 5°KH to 7°KH but those who are prepared to monitor their KH and pH more often can use a lower value of KH if they wish.

    After that, the water will be sterile and have a suitable KH/pH so it could be used straight away. A link to the correct DPD4 method that will verify that any chlorine or bleach that was used to sterilise the water has been fully removed is on my website here:
    http://www.mankysanke.co.uk/html/questions_answered.html
    OK mains water through chlorine filter it is then!!

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