Thread: simple rain water filter

sorry to start another thread so quickly... to be fair, this is a different subject to my other one

I was thinking of water costs recently and, noticing rain pouring off my polycarbonate pond roof, I started wondering. I know that rain isn't ideal as it can be acidic, too low in minerals, carries dust etc but has anyone ever built a sort of combined filter/trickle device containing oyster shells? I was thinking that I could add a gutter along the back of the roof and fill the vertical length of drain "down" pipe with shells with it draining directly into the pond and/or a water butt. Wouldn't the shells filter and remineralise/neutralise the rain water? I guess ideally I'd need a filter to stop larger bits of debris getting into the pipe also.

I realise that this doesn't help if there's a spell of dry weather but it could certainly prove useful at certain times of year surely?

I expect someone must have done this already so just after comments from someone who has tried it really...

well yes, I guess rainwater is the main one but also leaves, shade from the sun etc... I think a lot of people cover ponds to try to disguise from herons also.

What contaminants are you talking about specifically? (bearing in mind it's a fairly clean polycarbonate roof)

Part of my thinking here is that my tap water contains plenty of substances that don't seem ideal, even if run through a carbon filter.

This study seems to indicate that oyster shells can absorb "stormwater" pollutants.

Originally Posted by clippo

well yes, I guess rainwater is the main one but also leaves, shade from the sun etc... I think a lot of people cover ponds to try to disguise from herons also.

What contaminants are you talking about specifically? (bearing in mind it's a fairly clean polycarbonate roof)

Part of my thinking here is that my tap water contains plenty of substances that don't seem ideal, even if run through a carbon filter.

This study seems to indicate that oyster shells can absorb "stormwater" pollutants.

I have been led to believe that oyster shells only start to decay effectively when acid levels are high and at a very low level of efficiency. I would have thought it was better to store the run off into an IBC where the water quality can be tested and made safer before use with sodium bicarbonate, run through a reed & gravel bed filter, activated carbon, heavy metal filters as required.

This store of water after testing could then be used to clean filters, sieves or drums ( which ultimately go straight to waste)as I have done myself in the past, or even an emergency supply when topping up.

My own IBC supplies from rainwater capture are currently not used since completion of my new pond, but the intent to incorporate the supply again in the future once I have worked out an inclusion into a reed bed filter to the main filtration.

Originally Posted by clippo

sorry to start another thread so quickly... to be fair, this is a different subject to my other one

I was thinking of water costs recently and, noticing rain pouring off my polycarbonate pond roof, I started wondering. I know that rain isn't ideal as it can be acidic, too low in minerals, carries dust etc but has anyone ever built a sort of combined filter/trickle device containing oyster shells? I was thinking that I could add a gutter along the back of the roof and fill the vertical length of drain "down" pipe with shells with it draining directly into the pond and/or a water butt. Wouldn't the shells filter and remineralise/neutralise the rain water? I guess ideally I'd need a filter to stop larger bits of debris getting into the pipe also.

I realise that this doesn't help if there's a spell of dry weather but it could certainly prove useful at certain times of year surely?

I expect someone must have done this already so just after comments from someone who has tried it really...

I have two downpipe collectors piped into my pond. They enter into the drum and any debris will be removed there. My pond is anoxic filtered and has zero, yes zero, water added other than the rain water which I estimate will be the equivalent of two complete changes per year(with average rainfall). I live in an extremely hard water area and the pond is surrounded by limestone walls so I have never managed to record a pH below 7.5. You would certainly need to monitor pH levels but in 3 years I have not really found any movement. Nitrate levels are stable around 20-25ppm and I am probably slightly overstocked by most measures. I know most here are very nervous about using rainwater and maybe I would be if I had invested thousands in my stock but I haven't and am very happy so far.