Drainage issue. HELP !!!

[Mike8t1]

Hello Everyone
My name is Michael and i am new to reno's. I have just had a granny flat built in the backyard of my investment property. I have been told by council to build a path to the front door. The property slopes downward gently from front to back. The Granny flat is at the very back and sits perpendicular to the slope direction. As you can imagine when it rains the granny flat slab catches the water square on as it flows through the property. Ok so my issue, i am building the path (roadbase, pebble and stepping stones) at the exact same point in which the water hits the slab and kind of collects the water. Im interested to know how you guys would solve the drainage issue. Should i create a slope to have the water follow? Should i use irrigation (expensive option possibly?) Any info of feed back would be greatly appreciated. Thank you
Michael Henry

 

[Tools]

Install a strip drain at the junction between the two and run it to your stormwater system.

Tools

 

[allmine]

In Addition to above, ensure the last metre or so path sloops away from the flat, to the drain your fitting.
Also depending on volume of rain water, will depend on how long the drainage grate is, or perhaps 2 of them. The 300 m square types are easy to fit, available in shallow depth for easy fitting to, means you don't have to dig so deep for the pipe work to go.
If the water is prone to sitting against the slab the flat is on, then you may need to introduce some shallow aggy pipe in drainage gravel with water proofing plastic between this and the slab. this is to premote water to stay away, or, alternatively, just be sure the ground slops away from the slab for at leats 1m on the side where the water comes from.

Hope this helps.

 

[Mike8t1]

Thank you for the replies guys much appreciated.
I was curious as to where i can get the drain pipe stuff from cheaply as possible? I have seen it at bunnings but its expensive as. Some one mentioned ag pipe. Is this slotted ag pipe or would i need to cut the top off sealed ag pipe. Size wise would 100mm be big enough.
If so would i dig a trench around the slab (where the water currently pools) lay the slotted ag pipe in there, connect it to the storm water and bury it with a loose material of some kind???
Last bit, when the granny flat was built im pretty sure the roof drainage runs into the downpipe then away from the flat a few metres (buried in bluemetal) then into nothing. Should this be connected to an outlet of somekind??
Guys you have shed so much light on this topic for me already any more help would be fantastic.
Cheers
Michael

 

[willair]

I was curious as to where i can get the drain pipe stuff from cheaply as possible? I have seen it at bunnings but its expensive as. Some one
If so would i dig a trench around the slab (where the water currently pools) lay the slotted ag pipe in there, connect it to the storm water and bury it with a loose material of some kind???

That would work, just lay the ag pipe in the area's that the water lays, for the materials try a plumbing supply company they are a lot less in costs to bunnings,just ring around first and get the quotes then bounce them off each other..imho..willair

 

[allmine]

Thank you for the replies guys much appreciated.
I was curious as to where i can get the drain pipe stuff from cheaply as possible? I have seen it at bunnings but its expensive as.

Go to Tradelink, they are cheaper, or if the same price, will have better quality gear.

Some one mentioned ag pipe. Is this slotted ag pipe or would i need to cut the top off sealed ag pipe.

Ag pipe is black coloured flexible slotted pipe.

Size wise would 100mm be big enough.

You may find 75mm to be big enough, to connect it to the 90mm or 100mm pipe, duct tape is usualy all that is used.

If so would i dig a trench around the slab (where the water currently pools) lay the slotted ag pipe in there, connect it to the storm water and bury it with a loose material of some kind???

This is correct, use 20mm gravel for this, known as drainage gravel from the sand soil supplier.

Last bit, when the granny flat was built im pretty sure the roof drainage runs into the downpipe then away from the flat a few metres (buried in bluemetal) then into nothing. Should this be connected to an outlet of somekind??

That will be what is called a "storm water pit", over time they fill with other sediment and then need to be re-made, or cheat by plumbing into a drainage outlet.

Guys you have shed so much light on this topic for me already any more help would be fantastic.

Just try to keep in mind volumes of pipe work, so that is to say, how much water already goes down the pipe before I add to it?

Cheers
Michael

Cheers
Glad to be of assistance

 

[Mike8t1]

WOW thank you all so much. I think im set to get this fixed, just one last bit i'd like to clear up.
If my ag pipe leads to a dead end or "drainage pit" Will this allow the water to contine to run off of will it pool there under ground?
All in all guys thank you so much. Fantastic info
Cheers
Michael

 

[Rockstar]

WOW thank you all so much. I think im set to get this fixed, just one last bit i'd like to clear up.
If my ag pipe leads to a dead end or "drainage pit" Will this allow the water to contine to run off of will it pool there under ground?
All in all guys thank you so much. Fantastic info
Cheers
Michael

Can you show us a photo Michael? I have a drainage pit for my PPOR and it has been functioning fine for 7 yrs. I was wondering if the Granny flat was put through council they usually would ensure that you have designed an adequate stormwater management system? Also if there were water problems then it should be the builders or plumbers responsibility to rectify.

 

[Mike8t1]

Hey all. So i have provided some pics for you to see. These are of the trench i have dug to lay the ag pipe.
1)Should the trench be deeper?
2)Do i lay some blue metal 1st then the pipe then more blue metal?
3)How deep is too deep before the water stops seeping through the ground into the ag pipe?
4)I will have a 50mm layer of whacked road base over the blue metal and earth followed by pebbles and stepping stones. Will this still work?
5) Do you have to wrap the ag pipe in something before submersing it in blue metal?

Thanks for you help everyone, im looking forward to more solid info
Cheers
Michael

 

[willair]

Hey all. So i have provided some pics for you to see. These are of the trench i have dug to lay the ag pipe.
1)Should the trench be deeper?
2)Do i lay some blue metal 1st then the pipe then more blue metal?
3)How deep is too deep before the water stops seeping through the ground into the ag pipe?
4)I will have a 50mm layer of whacked road base over the blue metal and earth followed by pebbles and stepping stones. Will this still work?
5) Do you have to wrap the ag pipe in something before submersing it in blue metal?

Thanks for you help everyone, im looking forward to more solid info
Cheers
Michael

NO 1 layout the trench,have maybe 200 mill below the pipe work in b-m
NO2yes
NO3 I would start at 100mm,then work out the fall into the storm water
No 4 just use the blue metal-imho-
N0 5 depends on the site,but what i do is wrap the first 3-5 mts if it's in a heavy walk area..imho willair
This is not advice, i have not worked in the plumbing game for 10 years so things may have changed......

 

[battler]

The levels are hard to work out from the pics, but generally floor level has to be a minimum of 150 mm above finished ground level, and this is where you should be starting from. There should be no "pooling" near the building.

 

[Chatto]

As long as you have fall in your trench then it will not pool and will run to storm water, consider putting a pit drain in as well.
Throw some plastic down, in the trench as well and then backfill with your blue metal (20mm).
Work out the levels for your pavers with string line, concrete them down and then cover surronds with decorative 20mm.

Have fun, pump up your wheelbarrow!!

 

[Mike8t1]

NO 1 layout the trench,have maybe 200 mill below the pipe work in b-m
NO2yes
NO3 I would start at 100mm,then work out the fall into the storm water
No 4 just use the blue metal-imho-
N0 5 depends on the site,but what i do is wrap the first 3-5 mts if it's in a heavy walk area..imho willair
This is not advice, i have not worked in the plumbing game for 10 years so things may have changed......

Thanks for the replies For the trench to have fall, can i start at the middle (in the pics it is where the water meter is) and have it fall to either sideI was not going to connect to storm water as i do not know where it is. Having said that the guttering/down pipe does not meet storm water either. When the building was being done I saw a big trench with the down pipe extended to sit in the trench, then it was covered in blue metal. Is this what you would call a drainage pit or pit drain? Would you only use blue metal and not road base? Can you whack the the blue metal to be tight to avoid movement and the paver movin on top of it?

The levels are hard to work out from the pics, but generally floor level has to be a minimum of 150 mm above finished ground level, and this is where you should be starting from. There should be no "pooling" near the building.

Water pooled from day one after big down pours which is why iam where i am. The builders may have stuffed something up

As long as you have fall in your trench then it will not pool and will run to storm water, consider putting a pit drain in as well.
Throw some plastic down, in the trench as well and then backfill with your blue metal (20mm).
Work out the levels for your pavers with string line, concrete them down and then cover surronds with decorative 20mm.

Have fun, pump up your wheelbarrow!!

I like the plastic idea, so all in all so long as i am going 150mm or deeper below my ground level (befor road base or pebbles) i should be ok

Can anyone else see any probs here. Is whacked road base the way to go or would blue metal be best? Cheers for you intrest and assistance
Happy easter
Michael

 

[allmine]

Thanks for the replies

Can anyone else see any probs here. Is whacked road base the way to go or would blue metal be best? Cheers for you intrest and assistance
Happy easter
Michael

I not sure what your refering to with this question, but, what I would do is.....
1. Have your trench leeding the way you need it with its level (s). Either dirrection as you mentioned, so long as you have somewhere for the water to go.
2. Line it with plastic, drainage plastic can be got easy
3. a thin layor of 20 mm drainage gravel
4. then lay the agg pipe
5. fill over the agg pipe with drainage gravel till it is covered
6. then settle this down ready for the weight over the top, ie, pavers. If you don't "Pack" the gravel in, you risk the agg pipe collapsing, yet, don't crush the agg pipe either, somewhere in between if you catch my drift here
7. Now the road base, levels for the paving.

Now a place to send this water to?
Well, I think it would not be wise to connect to your granny flat existing storm water, it sounds like it is plumed to its own pit. If you connect this new agg pipe to this storm water, you risk more rain water being there then you have now, meaning, your new agg pipe becomes a 2nd pit!

Suggestion could be to run it off into another trench also. Not seeing the whole yard, I am not sure of an answer to this possible trouble.
Have fun?????????

 

[handyandy]

Definitely run the trench of into its own pit ptherwise there will be nowhere for the water to go.

Any drainage we have done will always include geo cloth both surrounding the ag pipe (sock style) and around all the blue metal. We do this by lining the trench with geo cloth then put a 50mm layer of aggregate to hold down the geo cloth and then the ag pipe on top of this. then you fill with aggregate inside the geo cloth up to the appropriate level and wrap all the aggregate with the excess geo cloth. Finish with more aggregate top of the total package. Then finally back fill with dirt.

The geocloth will stop the silting up of the aggregate.

I would think that the 150mm you indicate is hardly sufficient amd have found article that indicate 500mm should be the depth aimed for.

http://www.abc.net.au/gardening/stories/s908557.htm

There are many other references around.

Cheers

 

[battler]

Mike, re your question regarding bluemetal or road base,if you use compacted road base around the drain this will eliminate most of the absorbtion, so get you drain as low as you can,and plenty of bluemetal, scoria etc around it. In order for this drain to work it needs to be able to collect the water in the first place.

If you are going to compact and pave above the drain, effectively sealing it, I can't see that you will gain anything.

 

[Rockstar]

If you are going to compact and pave above the drain, effectively sealing it, I can't see that you will gain anything.

I totally agree. You're trying to get excess water away so don't seal up the drain. I wouldnt be lining with plastic either but using geotextile fabric to prevent silting up the drain.

Get your falls right and then line the trench with geotex. Then fill bottom first with 100mm of aggregate(blue metal) then place the ag pipe on this. Then fill up to the top with blue metal. Then cover with geotextile. Then lay and pack river sand base (it will still drain despite being packed). Then screed to required levels and lay pavers to have them falling away from the house. Can't tell about the rest as would need pics of the sides of house to assess where to direct water.

The main thing is to get both the surface and subsurface water away from the house.

 

[Mike8t1]

Ok so this weekend i will give this thing a crack. Based on the info so far i will be:
*Using ag pipe buried in blue metal wrapped in geo textile fibre stuff to stop the silt build up
*Creating a slight fall following the same direction of the land to give the watersome where to go.
*Digging the trench 500 deep and 300 wide leading to a drainage pit/rubble drain/soakaway (as i have no access to storm water)
*Using roadbase over the rest of the path with the exception of over the blue metal
*covering the sub level with stepping stones and then pebbles

Am i on track?? How big should the pit be? Would it be bad to have it near one that is already there for the drainage for the granny flat guttering? Thanks again all i have learnt so much from all those helpful people on here.
Regards
Michael

 

[craigb]

Definitely run the trench of into its own pit ptherwise there will be nowhere for the water to go.

Any drainage we have done will always include geo cloth both surrounding the ag pipe (sock style) and around all the blue metal. We do this by lining the trench with geo cloth then put a 50mm layer of aggregate to hold down the geo cloth and then the ag pipe on top of this. then you fill with aggregate inside the geo cloth up to the appropriate level and wrap all the aggregate with the excess geo cloth. Finish with more aggregate top of the total package. Then finally back fill with dirt.

The geocloth will stop the silting up of the aggregate.

I would think that the 150mm you indicate is hardly sufficient amd have found article that indicate 500mm should be the depth aimed for.

http://www.abc.net.au/gardening/stories/s908557.htm

There are many other references around.

Cheers

i agree with the depth but dont under mine your footings? isnt there a down pipe near by?

 

[allmine]

Hi Michael
I've re-read above, I see the chance for confusion a little here for you, I'll try to sort it out.

Ok so this weekend i will give this thing a crack. Based on the info so far i will be:
*Using ag pipe buried in blue metal wrapped in geo textile fibre stuff to stop the silt build up
The plastic I recomended is to go in the trench 1st, this catches the water and ensure it leads to the agg pipe rather then soak through deeper and continue your troubles. So I would lay this in such a way so that it catches the water from close to the slab and then allows it to "soak" down hill to the agg pipe.
Now fit the agg pipe and 20mm gravel. TAPE THE OPEN END UP WITH SILVER TAPE, STOPS GRAVEL GETTING INSIDE.
Once you have covered the agg pipe in 20mm drainage gravel, then cover all this in geo fabric, this is to stop silt getting into the drainage system. The idea is in 10 years, you service this cloth easily with out to much trouble.

*Creating a slight fall following the same direction of the land to give the watersome where to go.
I'm assumeing your refering to the agg pipe soak trench here, Good, you have it right here.
Then when you join the agg pipe to storm water pipe (if required)(use silver tape again here), it will need to continue going down hill also (stateing the obvious).

*Digging the trench 500 deep and 300 wide leading to a drainage pit/rubble drain/soakaway (as i have no access to storm water)
The trench size sounds good to me. The above storm water pipe is only mentioned as I do not know distances involved to the pit/rubble trench.

*Using roadbase over the rest of the path with the exception of over the blue metal
You can put the road base over the geo fabric, that is OK. Just make sure this has a slop leading away from the dwelling slab.

*covering the sub level with stepping stones and then pebbles
That should look OK, if the the road base is packed smoothly it will catch the flooding water and allow it to run off.
By me saying "packed smoothly" I mean this: it is not whacked with a compactor machine, but rather screeded smoothly, this screeding action firms the road base up, with out risking damage to the geo fabric etc.

Am i on track?? How big should the pit be?
Hummmm? I'm not to sure to be honest, try this:
How much surface area is the granny flat?
How much surface area is the area you need this drain for?
Now, how big is the existing pit?
You see the math here?
Would it be bad to have it near one that is already there for the drainage for the granny flat guttering?
Now, I don't see this as a problem, anyone else care to comment?.

Thanks again all i have learnt so much from all those helpful people on here.
Regards
Michael

Cheers mate, I'll be doing much the same myself this weekend, if it don't rain.