Monday, 17 February 2020

Nice Butt

This weekend I had to learn all about rainwater collection systems. You might have seen big green water butts standing innocently next to guttering downpipes. What I didn't know is that they're evil, and that they're biding their time until they try to knock your house down. I assumed that the guttering downpipe fed into the butt, and that it then had an overflow that fed into a second butt, or back into the guttering. I was wrong. The "diverter" that you let into the downpipe has a weir in it, and an airtight pipe to the water butt. Water can either flow into the butt, or over the weir and down the rest of the downpipe. There are a couple of reasons why this system is better than mine. The pipe to the downpipe can be small and flexible, if the flow down the downpipe overwhelms the capacity of the flexible hose, then the rest of the water just goes over the weir and down the rest of the downpipe.

It's a great system when everything is new. Now imagine that this water butt (which weighs 160kg when it's full) has been out in the garden for a few years and has been subject to hundreds of hour of UV degradation and dozens of frosts. Either the crappy plastic stand breaks and you don't replace it with something exactly the right height, or the flexible hose perishes. If the butt has been lowered by more than a few mm then the top of the butt is below the weir and all the rainwater flows down the side of the butt. If the flexible hose has perished the same thing happens. You are now collecting all the rain off your whole roof and funnelling it into one corner of your patio to try to undermine the foundations of your house.

I suspect that there's a better system where all the rainfall for an entire town is gathered together. It could be filtered and treated on an industrial scale until it's drinkable and doesn't bread lava and bacteria and then it could be piped back to individual households who use as much or little as they see fit - no matter how much or little rainwater their roof collects... Oh wait...

Richard "mains water" B

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