Using Storm Water of DVW Pipe for low pressure transfer

Just look up the manufacturers spec sheets.

20 metres will provide about 196 kpa static head, your choice of the connecting fire hose diameter size and length and nozzle size will add to the overall dynamic head loss. It is usual to work to a required flow rate through the nozzle once you calculate these losses. This will then give you the appropiate pipe size.

Many people also don't think it necessary to calculate the pipe length for friction loss if the pipe is running downhill. This is wrong.

Aaah...yes.

Thanks for the info. I need to run upto 40 sprinklers in total (25 butterfly on the house and 15 impact on a ring 10m out). Adds up to just short of 700L/min if everything is on at once and I need to end up with a minimum 150kpa for the sprinklers to operate.

I asked a supplier about DWV pipe and they said it wasn't pressure rated. I can get rural poly in 75mm, so I may do that and lay two lengths.

Thanks SBD

You may be better to use Class 12 Pressure Pipe. 200 kpa (or minimum of 150 kpa) is not a lot of pressure for sprinklers, so if in doubt I reckon that you should go for a larger diameter pipe.

It would be a mongrel to go to all the effort and expense to set it up and then find that you don't have enough pressure or volume to operate all the sprinklers. If there is a big fire approaching you will want as much water as possible.

Good luck cobber