drainage from roof

[Andy Mac]

Hi there,
Looking at alternatives for where/how to plumb roof water drainage from guttering on the extension. Can't afford a tank which would be the best option, so I really need to plumb the outflow away from the foundations (stumps).
The problem is the cutting made into the gradient, as this dictates how deep the stormwater pipe is put. The lower end of the cutting is not an option as there are too many other services to contend with. As I see it the possibilities are based around burying the pipe right under the cutting then bringing it up somewhere away in the original contoured ground...which means a section of pipe will always hold water, like an elbow under the sink (pictured).
Any problems with this? Is it kosher, or should there be some valve or screen to stop mossies etc, or stale water?! Any thoughts welcome.

Cheers,

[silentC]

I don't think there's any problem with it. All of my storm water pipes are permanently full of water (I hope). Mossies can't get in because it's sealed to the tank but there's nothing stopping you putting a flywire vent over the end of it.

[bricks]

It's done all the time,

• Use 100 pvc (heaps tougher) and leave an open junction up high on the d/p to act as an overflow
• Put an inspection fitting at the lowwest point in the path around the building so you can open it and clean out any muck that might get in there.
• You should use mozzie wired vent caps at entry and exit (mesh screen)
• You should seriously consider the use of gutter guard type product for the roof, this will help prevent the inflow of rubbish.

Do not use the aggregate pit as the water will try to run under ground and will probbably end up back at the footings anyway.

Cheers

Any more questions just ask

Bricks

[bitingmidge]

I know you've said the lower end of the cutting is not an option, but I'd have to see it in plan before I believe you!

Hopefully you've got enough fall in the cutting to drain surface water away?

As you have drawn it, you will have two problems in extreme conditions, the gutters will overflow earlier than they would otherwise because of the head that the downpipe has to overcome, and at the same time, when the pit is fully charged, it's on the high side and you'll have to ensure that water doesn't flow back against the house as well. You could also find that you have a spring appearing out of your batter!

Have you thought of running a simple spoon drain to the ends of the house and disposing of it from there?

Cheers,

P

[MonkeyWrench]

Can't afford a tank which would be the best option, so I really need to plumb the outflow away from the foundations (stumps).


You would still need to install storm water drainage even if you had tanks because when the tanks are full the subsequent water will have to go somewhere.

[Andy Mac]

Thanks for the replies! I may be on the right track afterall.
I didn't think of water soaking back through the ground to the cutting/batter, which will be a fairly steep retaining wall on each side. And the whole idea of head to overcome...certainly didn't think of that! All I can say is both gutters run along verandahs, so if they overflow its not a great concern! And I know tanks need an overflow, our small one is so fitted. Would be simpler if there was only the one to consider...
The low end of the cutting is where the original house is, the new one is 90* to it. There is some fall around the new house, but still some levelling to do, and a small spoon drain to take any buildup away. It will come from under the deck of the breezeway between the houses, I just don't want to overload it with full flow from the gutters.

Cheers, thanks once again.

[ian]

Andy
as I interpret your cross section, the house is in a hole
you have to drain the whole hole to somewhere, and slope it away from the building (otherwise your house will end up sitting in a bog hole)
drains around the top of the hole wont be good enough
so run the gutter drainage out the same discharge points you use for the surface drainage (maybe on the same line as your proposed dish drain but underneath it — any other services should be much deeper than the 100mm or so cover you will need to the storm water pipe)



ian