Working out falls - 1:40

[scooby]

1:40 fall is 25mm per meter,correct? but if a drain run is lets say 16ms useing 150mm supersleve clay pipe (each pipe is 1.75ms long) what is the correct amount of fall on each pipe ,and how do you calcalate the measurements,would be grateful if you could show me how its all worked out.cheers

[steve r]

A fall of 1:40 is equal to 2.5%.
So 1000mm (1 metre) x 2.5% = 25mm, as you rightly say.

16000mm (16 metres) x 2.5% = 400mm total fall.

1750 (1.75 metres) x 2.5% = 43.75mm fall for each pipe.

It may be easier to lay all the pipes to a string or laser line than working out the fall for each individual line.

[flowjoe]

1:40 fall = 25mm per metre of pipe
16mtrs x 25mm = 400mm of fall
16mtrs divided by 1.75mm pipes = 9.1pipes
400mm of fall divided by 9.1 pipes = 43.9mm per 1.75mm pipe

1:60 fall = 16.6mm per metre of pipe
16mtrs x 16.6mm = 265.6mm of fall
16mtrs divided by 1.75mm pipes = 9.1 pipes
265.5mm of fall divided by 9.1pipes = 29.1mm per 1.75mm pipe.

Now strap a block of wood to the end of your 1mtr level allowing for the width of your sparky tape to reach the desired thickness and your away, or by a laser level.

Disclaimer
The above calculus was concocted during a second glass of grape juice
:p

[scooby]

thanks for the reply guys, has helped.