Rainwater drainage

[Neo Cortex]

Hey forum, I am interested to know what is the correct way to manage rainwater for a build that I am working on. Can I get some general advice and guidance on what to do with the water that the gutters collect please?

Many thanks

 

[DAZB]

The gutters should carry the water to a drain via the drainpipes, do you not have any drainage below ground ? If you are wanting to harvest the water for use in the build then a good idea is to direct the water to a series of IBC tanks to store it and use as you need it.

 

[Murdochcat]

How do the existing gutters drain atm ?

 

[Cheslea2010]

Rainwater needs to be discharged into a surface water system such as a soakaway or rainwater harvesting system. You cannot connect surface water systems to mains sewerage.

 

[noseall]

Hey forum, I am interested to know what is the correct way to manage rainwater for a build that I am working on.

First choice is always independent soakaway, 5m from the building.

Second choice is dedicated storm system.

A last resort is to use the foul drain system, if ground conditions are unsuitable (clay or steep terrain etc) and there is no alternative storm system. You may need to check with your water company, that you may already be paying a storm handling charge.

 

[Neo Cortex]

It’s a completely new building. 6m x 9m with a flat roof. I just want to get rid of the water that lands in the roof and ends up in the guttering. I had a look at how it is done on the house and there is a trap that catches the gutter output with a little notch in it so that if it blocks it overflows into the sewer. See attached picture. I am looking to do something like this (let’s ignore the state of maintenance ). I am interested to know what this looks like underground. How deep / how wide / how to construct it etc.

 

[freddiemercurystwin]

As mentioned you're first choice should be to drain it into a soakaway, are there reasons you cannot do that?

 

[Ivor Windybottom]

The overflow into the sewer looks like a good idea until you think about it... It could go the other way - if the sewer was blocked you wouldn't know, and raw sewage would run into the rainwater system. This could block perforated pipes and soakaways, contaminate the ground and severely stink. It would also mean that you wouldn't be aware it was happening as it would appear to be functioning normally, i.e. the bog would flush and the sink would empty.

 

[Murdochcat]

If you’re doing a soak away make sure the BCO sees what you are planning to do before you start digging

 

[Neo Cortex]

As mentioned you're first choice should be to drain it into a soakaway, are there reasons you cannot do that?

 

[Neo Cortex]

The overflow into the sewer looks like a good idea until you think about it... It could go the other way - if the sewer was blocked you wouldn't know, and raw sewage would run into the rainwater system. This could block perforated pipes and soakaways, contaminate the ground and severely stink. It would also mean that you wouldn't be aware it was happening as it would appear to be functioning normally, i.e. the bog would flush and the sink would empty.

I’ve had the house with this setup more than 15 years. It’s been fine never once had a problem with it in terms of draining rainwater. The sewer end has a U bend on it so there’s no way it can come back up. If the grid on top blocks it overflows into the sewerage. The drain did block once it came out the manhole cover as the manhole cover is in a lower position. I am interested in this type of setup as I’ve seen it work and have confidence in it. Just need to know what happens to that rainwater once is goes down the hole. Presumably there’s a long pipe / well going down there with many holes around its sides so the rainwater can filter out into the land around it?

 

[Ivor Windybottom]

I agree it looks like a good idea... on the face of it.

The manhole cover probably won't leak as fast as a toilet flushes. The U bend is no obstacle, it will work just as well in either direction.

I'd be interested to hear what a building inspector thinks though.