# Thread: 3/4" Mop-Up Lines PSI/GPM?

1. ## 3/4" Mop-Up Lines PSI/GPM?

What is the correct PSI for a 3/4" line when using a standard brass combo nozzle? What about any other types of 3/4" nozzles?

For all other lines tips should be at 50 PSI and Combo/Fog nozzles at 100 PSI.

But it looks like the 3/4" nozzles require alot higher pressures, and I can't find much info out there. The manufacturer for a brass combo 3/4" nozzle states it shuts down when pressure drops below 250 PSI.

Thanks for any help!

2. ## MFG update

The manufacturer responded that the 250 psi spec is for static pressure (non flowing). With a flow psi of 100.

So looks like FL & PSI for 3/4" lines should be calculated just the same as larger lines.

3. ## Coefficient.....

If memory serves me correct, the coefficient for 3/4" is 1100 but check what the manufacture recommends. So..... Take the coefficient and multiply that by the highest flow gpm of your nozzle (divided by 100) squared. Multiply that by 1 (100' sections divided by 100) and add that number to 100. C Q (squared) L

Example: 3/4" flowing 25 gpm
1100(.25 x .25) X 1
1100 x 0.063 x 1 =s 69.3 or 70..... per 100'; so 100' of 3/4" with combo nozzle @ 25 gpm is: 70 + 100 =s 170

Seems pretty high for hard-line or pee-line but reduce the FL by upping the size of the line to 1". Still a good mop-up line, easy to manage and can be restocked at Base Camp.

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