Rainwater harvesting and SUDs questions

wild edgeswild edges The north west of south east WalesPosts: 2,905
You may be aware that building legislation is changing in new housing to make sure all new development (including extensions to existing houses) is designed to manage rainwater on site rather than send it off downstream to flood other areas. SUDs stands for Sustainable Urban Drainage. This has got me wondering what people do in their gardens to manage rainwater. I imagine a lot of gardeners will collect rainwater in butts to use but has anyone got more creative?

In my garden all downpipes go to some kind of collection tank with overflows that go back into the drains. I've got about 1500 litres of capacity on the downpipes plus another 500L storage in useful places. In the summer all the water gets used in the garden or to wash the cars but in the winter I connect a hose to the taps, run the hose to the drain and set the tap to drip at a rate that empties the tank before the level usually reaches the overflow. The drains from the houses here all discharge into the local stream.

My ambition is to eventually have water troughs that I can use as mini planted ponds that will intercept the water before it gets to the tanks to further slow the drainage rate. I haven't quite worked out the plumbing for this yet as I'd like a sediment trap before the trough as the water tanks are getting a bit disgusting at the bottom after a while. The moss on my roof is probably the cause of that. My plan is that the troughs would have around 60 litre capacity when full and always be at least 1/3 full with a weir coming from the trap to agitate the water. I'd need 2 overflows : 1 at 1/3 height that flows very slowly and one at full height which has the same diameter is the inlet pipe. Plants would just be cuttings from whatever is getting too big in the pond (a lot of water mint probably).
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  • Blue OnionBlue Onion Posts: 1,783
    Why not just have the water troughs after your waterbutt system, having your winter hose fill them instead of the drain?  They would be seasonal, and easier.. many birds and other bits of wildlife would enjoy the winter water (if you kept it from freezing).  You could still put the sediment traps between your spouts and tanks.  
    Utah, USA.
  • raisingirlraisingirl East Devon, on the Edge of Exmoor.Posts: 3,442
    We've used storm cells a few times - this type of thing https://www.plasticdrainage.co.uk/brett-martin-rainbloc-soakaway-crate.html (there are a number of makes available from most good plumbing outlets.) They are strong enough to sit under a patio or even a drive if you get the right ones. Basically they would just be extra storage in your system.

    The best 'natural' option I think are swales; ditches that dry out completely in dry weather and fill with water in heavy rain, from which the water can soakaway into the ground slowly and never go into the drain. There are plants that will cope with this sort of environment. The advantage is that because they do dry out, the potential storm capacity is larger than an equivalent size partly filled ditch.

    The other thing to remember is that ground with a tree in it absorbs something around 60x more rainwater than grass or bare soil. So plant trees in your swales  :)

    My heart has joined the thousand, for my friend stopped running today
  • wild edgeswild edges The north west of south east WalesPosts: 2,905
    Why not just have the water troughs after your waterbutt system, having your winter hose fill them instead of the drain?  They would be seasonal, and easier.. many birds and other bits of wildlife would enjoy the winter water (if you kept it from freezing).  You could still put the sediment traps between your spouts and tanks.  
    I should have explained: My house is 3 storey with the main garden up at first floor level and all the water butts are down at ground level. My plot is 27 metres front to back and rises 6 metres in that space.  I'd want the mini ponds up at the garden level but I don't have space for the water butts up there. Plus if they were after the butts then they wouldn't really get any water in the summer as I'd be emptying the tanks before they overflowed.

    Freezing is my biggest problem as we're up at 1000ft above sea level and it gets very cold here.
  • SkandiSkandi Northern DenmarkPosts: 581
    edited May 2018
    The mind boggles with how one can catch all the water off of just one houses roof! I have one water tank (1200L) that takes water from 1/2 of one side of one of three roofs. It filled up in two days this month. a quick calculation shows that my roofs produce 263000L of water in a year I have never run the single tank dry (watering and duck baths) so have no use for any more water around my place!  My gutters just drain in the the ground which then eventually will end up in the drainage canal about 200m away. (impermeable clay layer under the soil here)
    In winter the tank is removed and stored in the barn it would just freeze solid if not.

    Edit it's been thundering today and we've had 6cm rain in a few hours that's 18700L That's an awful lot of water, no wonder my lawn is always wet.
  • BijdezeeBijdezee Bruges, BelgiumPosts: 702
    This house we moved into almost 2 years ago has a large tank for rainwater under the patio. It has come in VERY handy in dry periods. My DH put a hand pump on it. 
  • wild edgeswild edges The north west of south east WalesPosts: 2,905
    Skandi said:
    The mind boggles with how one can catch all the water off of just one houses roof!
    This is part of the problem. The regs require that the storm water collection allows for what they call a '1 in 100 year storm event' which sounds like something Noah would struggle to plan for.

    My roof is very small but for a big bungalow you'd need a lot of capacity to deal with the flow.
  • raisingirlraisingirl East Devon, on the Edge of Exmoor.Posts: 3,442
    edited May 2018
    This is part of the problem. The regs require that the storm water collection allows for what they call a '1 in 100 year storm event' which sounds like something Noah would struggle to plan for.

    Yeah, it's not really a 1 in 100 year event these days. It's a statistical calculation from average weather data in the UK and based on that rainfall happening for a very short period of time. I think the intensity of rainfall that it's based on actually happened twice in two years not long ago. Rainfall intensity is increasing with climate change, but that very heavy rain is usually happening in Summer, (thunderstorm causing flash flooding on the roads), not winter - which tends to be weeks of steadier rainfall causing rivers to flood. SUDS can't cope with the latter, usually, but it can help with the former.

    My heart has joined the thousand, for my friend stopped running today
  • Blue OnionBlue Onion Posts: 1,783
    Thanks for the further explanation.. that makes sense now.  :)  

    In Utah, it was illegal to collect rainwater up until 2010.. and now it is allowed at a residential home for personal use, but you must register with the state.  It's on my to-do list.. but the cost and general lack of rain has put me off so far (we usually average about nine inches of rain per year).  I have extensions on all my downspouts so they lead towards my grass or plants, so it's not really ever 'wasted'.  
    Utah, USA.
  • FireFire LondonPosts: 5,271
    I read recently that in many states it is / was illegal to have water butts. Astonishing!
  • Hostafan1Hostafan1 Posts: 20,540
    In many states it's illegal to be homosexual. Astonishing!
    Devon.
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