Moving rainwater from front of house to side

[Fred Bear]

I have three downpipes at front, side and back. At present back goes to 3x 210L water butts on flat roof and 1520L at ground level. Side and bathroom greywater goes straight to the ground in garden. Front which also drains neighbour's front roof (total about 40 sq m) goes to the ground and there is a diverter to a water butt by front door.

As part of a complete update I want to bring the water from the front to the side dp. My idea is to replace the 68mm dp with an 82mm pipe then T off with a 50mm pipe at a height of about 4m under the bay window cill then round to side. This pipe will need to be almost horizontal, about 12m long and include 4x 45deg and 1x 90deg bends.

I plan to use the lower section of the dp as a first flush device, so the water would first fill up the dp then overflow into the 50mm pipe reducing the chance of a blockage. Dealing with the water butt is a separate issue.

Because it is at the front Mrs Bear would like to keep it fairly neat but I am free to do anything round the side IYKWIM.

My question is: Will this be sufficient to cope with heavy rain, or will I need to provide for an overflow?

Any advice would be welcome.

[HouseHeat]

Always provide and overflow.  You never know what the weather is going to throw at you.

Mike

[Baz]

gutters are wonderful things that are all fitted with automatic overflows!
Like some more info about the first flush thing. How does it empty for next time taking the crud with it?

[knighty]

would it be easier/neater if instead of running the down pipe around the house.... you put a (nice looking) water butt at the bottom of each one to catch the water, and then ran a smaller pipe linking it up to your other water stock ?
(could be underground?)

[Fred Bear]

Thanks for your replies.

HouseHeat: That confirms my own thoughts Mike. The overflow will discharge into my porch gutter.

knighty: Some good ideas there which I hadn't thought of.  My problem is that my water butts are on top of my kitchen roof so without pumping I need to feed them from a height of about 4 metres. I want to keep them there to save space at ground level and allow them to supply a downstairs WC without a pump.

Baz: I haven't completely worked this out yet. I will block the bottom of the 82mm dp probably with an access cap, then add a valve and hose so I can empty the contents manually. Or I might feed the hose into an old watertight plastic drum (instead of a butt) with a vent above 4 metres (the height of the 50mm tee). Hope that explains my ideas.

I have already started work on the system but any ideas/comments would be welcome. I will post some photos when complete.

Fred

[Baz]

Since water levels out, provided you seal it you can go down to ground, across & round then up again in 3 or 4 inch giving a higher capacity pipe. Only potential problem then is  freezing.

[Fred Bear]

Baz: Thanks for that idea. To avoid most of the freezing problem I could take the pipe under the house (cellar and between ground floor joists. That would be very neat and the minimum pipe run. Would solvent weld waste pipe be suitable (leak proof)? The main problem as I see it would be silting up unless I used a filter on the front wall of the house.

[profp]

I have occasional issues with my reed bed pipework silting up - any recommendations for filters that work well with solvent weld waste pipe gratefully received. Fred - if I were in your shoes, I'd be happy with the water-tightness of solvent weld waste pipe, it's not as if the head is significant, but remember that it degrades in sunlight. If that is a concern, use blue-walled flexible PVC pipe (probably more expensive, but UV-safe & pressure tested).

[Baz]

You could have a T on the far side with  a bung and remove it once in a while before a storm to give it a flush through. The freezing problem is in the standing column each end. However as that only applies in winter and if it is wet enough perhaps you wouldn't need the front collection facility all year.

[Fred Bear]

Thanks for your help Profp and Baz. I am going to think through my options. Meanwhile: in the last 2+ months here in east London it has only rained twice IIRC and we have collected only about 150L from the back and side roofs. Greywater from our bathroom is supplying the garden and we haven't had to resort to the mains yet.

[Fred Bear]

I decided to go with my original plan, partly because I had already completed part of the work. Here is a photo of the front downpipe arrangement. The original 68mm downpipe has been replaced with an 82mm soil pipe. On the left is the 50mm tee round to the side. I managed to get a slope of 15mm per metre. On the right is the overflow into the porch gutter which is unlikely to ever be needed, but reassuring should there be a blockage.

[solar_cambridge]

What is the capacity and flow rate for drain off for the first flush section? looks like you are wasting at least 10 litres every rainfall?

[Fred Bear]

Been away on holiday for past two weeks - hence delay in replying. Using my solar powered calculator I have calculated that the dp holds 20 litres. Here is a photo of the base of the dp which would normally be hidden behind a water butt. I have a choice of running this off into the porch dp which empties onto the front garden or into the water butt. This is all manual of course but I think it is good enough for me.

[Fred Bear]

Here are the rainwater downpipes coming together at the side of the house and the 40mm pipe supplying the water butts on the kitchen roof.  If there was a cloudburst the excess rainwater that the 40mm pipe could not cope with would carry on down into the drain (grey 82mm pipe).

[Fred Bear]

Here is my attempt at a filter on the outlet to the water butts. If rainfall becomes too heavy, or the filter becomes blocked, the surplus will bypass the filter and go straight to the drain. Hopefully it will be self cleaning. What I want to check is whether 100% of normal rainfall is being collected.