# Forum Home Renovation Plumbing  Drainage issue and minimum depth of storm water pipes

## PaulKaren

Hi all, 
Been in our place a few months now and have been  waiting for our first decent rain to see how the gutters etc handle it. I bought the house knowing i have some drainage issues as water pools against the downstairs foundations under the house. Well most of the gutters backed up and overflowed within a few minutes of rain the other night (admittedly it was absoloutely belting down). Anyway my biggest concern is at the side of the house where i need to stop water from pooling and making its way to under the house/foundations. Not sure if there is a minimum depth for stormwater pipes but this one has been run more or less level with the foundation. Is this standard practice? I am going to install a water tank and divert water to the tank from the main gutter above the side of the house with the issue. I am then thinkink i will run the overflow from the tank all the way along the fence line down to the easement that runs to our pit (effectively bypassing the stromwater system for that gutter only. Therefore the pipe shown in the pics will only carry water from a pit that collects water from driveway run off. I believe this should help the problem but would like to be able to waterproof the foundation to stop water ingress even further. Problem is from reading on this site i would have to dig to base of foundation and instal agi line, gravel etc there which means i would be well below the storm water system and would then have to add a pit and a pump etc etc. The first photo shows the downpipe that will be removed and run to the tank etc.
2nd photo shows 100mm DWV stormwater pipe run at same level as foundation. Was even thinking i could make this part of that line an agi to catch more ground water and stop it making its way through to under the house? Any one got ay thoughts on all this? Any help much appreciated..Cheers...Paul

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## cyclic

You mentioned an easement. Check with Council if there is a storm drain in the easement that you may be able to connect to. 
As for rules on stormwater, they were, for a long time, almost non existent so any one could lay storm water pipes in a residence, hence, lots of problems later, but in saying that, it does not matter how deep you go  
as long as the pipes cannot be damaged in any way, eg cars, garden forks etc.. 
Always use 100 dwv for stormwater drains, do not use the thin 90mm rubbish. 
With regard to foundations, as long as the top of the ag drain is below the top of the foundation and draining off to a lower, unrestricted point, you should be ok. 
And contrary to popular belief, I do not believe it is necessary to use socked ag pipe, I never have.

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## PaulKaren

> You mentioned an easement. Check with Council if there is a storm drain in the easement that you may be able to connect to. 
> As for rules on stormwater, they were, for a long time, almost non existent so any one could lay storm water pipes in a residence, hence, lots of problems later, but in saying that, it does not matter how deep you go  
> as long as the pipes cannot be damaged in any way, eg cars, garden forks etc.. 
> Always use 100 dwv for stormwater drains, do not use the thin 90mm rubbish. 
> With regard to foundations, as long as the top of the ag drain is below the top of the foundation and draining off to a lower, unrestricted point, you should be ok. 
> And contrary to popular belief, I do not believe it is necessary to use socked ag pipe, I never have.

  Hi and thanks for that....there is a stormwater pit in the easement on our property that the stromwater runs in to. No problems there.  A few more questions though:
Would you remove the 100mm DWV that is there and replace with an agi to pick up run off or maybe leave the DWV and run an agi next to it? 
Is 100mm Stormflex UV stabilised as is 100mm DWV?  
I am thinking of buying 30m roll stormflex for tank overflow and running down fence for now..will be buried in garden later...is this ok or council wouldnt approve? 
Cheers again

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## Oldsaltoz

Any exterior walls that have soil against them (below ground level) should have been waterproofed during construction. 
The waterproofing needs to be applied to the wall and on the joint between the wall and the footing. 
The drainage pipe should be just below the top of the footing. 
The area above and just below the drain should be filled with a free draining gravel not less than 20 mm, (railway ballast stone is cheap). 
Existing fixed pipes above this drain can be left in place. 
Good luck.   :Smilie:

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## cyclic

> Hi and thanks for that....there is a stormwater pit in the easement on our property that the stromwater runs in to. No problems there.  A few more questions though:
> Would you remove the 100mm DWV that is there and replace with an agi to pick up run off or maybe leave the DWV and run an agi next to it? 
> Is 100mm Stormflex UV stabilised as is 100mm DWV?  
> I am thinking of buying 30m roll stormflex for tank overflow and running down fence for now..will be buried in garden later...is this ok or council wouldnt approve? 
> Cheers again

  I would bet it is not uv resistant but not sure as I have never used it. 
Why not just buy the dwv pipe and fittings you need and push them together without glue for a termporary drain, just don't push them in all the way. 
I am not sure if you intend to clip the temp drain to the fence but stormflex will not work in this case, it will fill up and sag then probably tear with the weight. 
As Oldsaltoz said, leave the existing drain and run a new ag drain because ideally, ag drains should always be seperate to any downpipe drains. 
As for Council, storm drainage comes under the Building Dept in most cases and Building inspectors are usually happy if there is some form of drain getting the storm water away 
 from the building/foundations, what I suggest is  do it once, do it right.

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## PaulKaren

> Any exterior walls that have soil against them (below ground level) should have been waterproofed during construction. 
> The waterproofing needs to be applied to the wall and on the joint between the wall and the footing. 
> The drainage pipe should be just below the top of the footing. 
> The area above and just below the drain should be filled with a free draining gravel not less than 20 mm, (railway ballast stone is cheap). 
> Existing fixed pipes above this drain can be left in place. 
> Good luck.

  Again thanks for the replies old salts and cyclic.....one last question: a full 20 litre drum of Bitkote no.3 was left here when we moved in (pity they didnt use more of it during construction!) Is this good enough to use as waterproofing for the walls/foundation? would i be wasting my time doing a few coats of this and then maybe putting some builders 
plastic down before layinfg gravel / agi pipes etc etc. Do i need the plastic and is bitkote the right stuff to use? Cheers again...

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## cyclic

> Again thanks for the replies old salts and cyclic.....one last question: a full 20 litre drum of Bitkote no.3 was left here when we moved in (pity they didnt use more of it during construction!) Is this good enough to use as waterproofing for the walls/foundation? would i be wasting my time doing a few coats of this and then maybe putting some builders 
> plastic down before layinfg gravel / agi pipes etc etc. Do i need the plastic and is bitkote the right stuff to use? Cheers again...

  Again, never used that particular product, but as long as it is brushable bitumen, it should be fine. 
Check with the manufacturer. 
I have never used plastic in an ag trench, simply pipe and stone.

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## Oldsaltoz

According to this link   http://www.lanko.com.au/lanko/images/product/12127.pdf 
It's much the same product as Sikaflex Sik-Tite BE. a bitumen emulsion based product. Make sure you read the instructions in the link above. 
Most bitumen emulsion based products like a 50% product to 50% water on a damp wall for the first priming coat, then 3 full coats. 
They should also be covered after curing with a protective board, I have used Core-flute with good results up to 6.50 m below ground. 
The Sikaflex product is redy for another coat after only 30 minutes so just about a non stop job as no waiting. 
The plastic core-flute sheeting eliminates the need for any plastic and prevents any damage when back filling with gravel. 
Good luck.    :Smilie:

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