Draining Charged Pipes to a Rain Water Tank

How to calculate the size of Charged Pipes draining to a Rain Water tank. Further detail can be found here
www.roof-gutter-design.com.au....
Charged pipes are necessary when an above ground tank is positioned away from the building, (or quite a distance from furtherest downpipe,) and the pipe must travel underground before rising again to discharge into the tank.
This means that water will always be trapped in this underground loop after the rainfall event. Hence the definition of being called "Charged".
Strangely there are no mention of such things in any plumbing code, as it is not strictly a stormwater pipe flowing under gravity, nor is it a water pipe flowing under pressure. so the powers that be started to ask some embarassing questions.
This Video attempts to shed some light on the subject by showing you how to design a pipe to the hydraulic grade line.

[@dtswk]

Thanks Ken for the amazing tool

[@ChinthakaVithanage]

Thank you Ken. Very useful tutorial.

[@fatimach2955]

Thank you for explaining well. We had this problem since we bought the house and 10 years ago and the system didn’t make sense to me as the tank doesn’t get water. Now we need to do something

[@TheHooon84]

Ken oath 👍

[@KrazyKajun602]

or why not increase the size of the gutter and reduce # of down pipes?

[@The123ks123]

sure that can be done, but it doesn't change the rainfall runoff. However, with this program you can have as many or as little number of DP's as you wish.

[@KrazyKajun602]

@@The123ks123 So how would I go to design a system for a 30x80 shed with 3/12 metal roof, 12' tall sidewalls with a location that gets 60" of annual rainfall. I live in central Louisiana, where 5"+ rains are common in a day.

[@The123ks123]

@@KrazyKajun602 You would have to look up the design rainfall for eaves gutters in your state. Your local Authority or Plumbing Code may give you some quidance. Inches per year, or inches per day is not suitable for this calculator.
You are looking for a rainfall intensity that can be converted to a flow in gals/min or similar.
There is a conversion calculator somewhere on the site to convert imperial to metric measurements.
If you can find that out you can use the DP program to get the roof gutter size, and the size and number of downpipes (leaders) that you require.
www.roof-gutter-design.com.au/Downp/applet.php
Then use the Charged pipe program to get the pipe size to your tank.
www.roof-gutter-design.com.au/ChargedPipes/ChargedPipes.php?v=2
I think our Australian design rules may be too different to yours.

[@Nerdificationing]

What if a charged pipe is cut during a renovation 😂 Can capping it be enough?

[@The123ks123]

If the pipe was capped, where does the rainwater go? If designed correctly it will overflow either over the front or the back of the eaves gutter.