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  1. #1
    Join Date
    Aug 2004
    Location
    sydney
    Posts
    62

    Default Stormwater - minimum fall?

    All,

    After searching the net for about an hour I thought I'd post the question here....

    I am looking to install a water tank under the deck and connect to the 2 downpipes at either end of the deck.

    Currently the pipes run thru the deck and into the ground.
    My plan is to cut them off and run them across under the bearers to the top of the tank (about 9m away).
    What is the minimum fall I need to have on the pipes to ensure a good flow?

    Cheers
    Geoff

  2. #2
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    3,208

    Default

    As long as there is slope you will have flow.
    Regards, Bob Thomas

    www.wombatsawmill.com

  3. #3
    Join Date
    Oct 2001
    Location
    Warwick, QLD
    Age
    45
    Posts
    1,175

    Default

    When I did the shed at my last house I was advised to have at least 5mm of fall for every metre of pipe/gutter.
    Have a nice day - Cheers

  4. #4
    Join Date
    Jul 2003
    Location
    Gorokan Central Coast NSW
    Age
    80
    Posts
    941

    Default

    Irrigation ditches in cotton fields have a fall of 1 foot to the mile.

  5. #5
    Join Date
    Jul 2000
    Location
    Drop Bear Capital of Gippsland (Lang Lang) Vic Australia
    Age
    74
    Posts
    2,238

    Default

    Currently having a sh!te fite with our council as our land is 3 metres lower than the drain, they still seem to think that water runs uphill, saga continues...
    Stupidity kills. Absolute stupidity kills absolutely.

  6. #6
    Join Date
    Aug 2003
    Location
    .
    Posts
    4,816

    Default

    Love the new avatar.
    Horse stops mid air, must be the council horse?

    Al

  7. #7
    Join Date
    Jul 2000
    Location
    Drop Bear Capital of Gippsland (Lang Lang) Vic Australia
    Age
    74
    Posts
    2,238

    Default

    Few years ago, it did, I didn't, 8 cracked ribs, 1 broken wrist.
    Horse suffered sore bum when I got home from hospital, re admitted, 1 broken foot.
    (last one was a lie)
    Stupidity kills. Absolute stupidity kills absolutely.

  8. #8
    Join Date
    Aug 2003
    Location
    .
    Posts
    4,816

    Default

    Is that you on the horse?
    I would have stopped too if I was the horse.

    Al

  9. #9
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    3,208

    Default

    Is that why yer ride donkeys now.
    Regards, Bob Thomas

    www.wombatsawmill.com

  10. #10
    Join Date
    Jun 2005
    Location
    Melbourne
    Age
    51
    Posts
    119

    Default

    A fall of 1 in 100 is adequate in a closed pipe situation, in a larger pipe (250mm diameter) you could go to 1 in 200. In an open gutter, where litter such as leaves and dirt could get trapped it would be safe to allow more like 3 in 100.

    Cheers
    Justine

  11. #11
    Join Date
    Jun 2004
    Location
    Bunbury W.A.
    Age
    56
    Posts
    294

    Default

    Have you given any thought to disposal if/when the tank fills up?
    if you always do as you have always done, you will always get what you have always got

  12. #12
    Join Date
    Aug 2004
    Location
    sydney
    Posts
    62

    Default

    maglite,
    The overflow is directed back into the stormwater channel...
    Geoff

  13. #13
    Join Date
    Jun 2004
    Location
    Port Sorell, TAS
    Age
    59
    Posts
    177

    Default

    People get carried away with this. If this section of pipe is below downpipes etc the 'head' of this water will push it through this section, even with reverse fall. To illustrate this better our last house had a syphon system: The kerb on the roadside was only about 1.5m below the guttering, but the pipe had to be about 1m below the kerb outlet as it was buried under the driveway. I sealed all joints, had an overflow on the downpipe, and it worked a treat. Note that the system is permanently full when not running.

    That said, most inspectors like to see 'normal' pipes sloping towards the outlet. Put a 'turn of the bubble' on it if you can.
    The only way to get rid of a [Domino] temptation is to yield to it. Oscar Wilde

    .....so go4it people!

  14. #14
    Join Date
    Apr 2002
    Location
    Brisbane
    Posts
    0

    Default

    The other answer is...... as much fall as you can practicaly get.
    If thats all the fall you have....
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  15. #15
    Join Date
    Jul 2000
    Location
    Drop Bear Capital of Gippsland (Lang Lang) Vic Australia
    Age
    74
    Posts
    2,238

    Default

    If it's likely to build up a retarding basin may be order of the day to save any problems.
    Thanks Al, just because I'm 5'2" and 55kg you have to make fun of me
    Stupidity kills. Absolute stupidity kills absolutely.

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