Head pressure questions

[jrlmsla]

Hi all,
Quick question. What happens to head pressure when you use a split lock line at the inlet? I haven’t been able to see anything related to factoring in one in calculations.

 

[Ron Reefman]

Head preassure is due mostly to the weight of the water in the vertical sections of the plumbing. Having a split at the nozzle in the tank won't have any effect. Of course I'm making an assumption your statement of, "...when you use a split lock line at the inlet..." means at the tank end, which I would call a nozzle or outlet.

 

[jrlmsla]

Exactly what I meant. Thanks for the reply

 

[Plecosam]

Pressure equals rho x gravity x height, there is no diameter (pipe size, inlet size etc) in the equation.

 

[ca1ore]

Head pressure is simply the height differential between two bodies of water. Pipe size, fittings and other flow robbing accoutrements add back pressure but are not technically head pressure.

 

[DCR]

Be careful with the semantics here. Frictional losses due to pipe and fittings most definitely affect the required head the pump needs to overcome for a given flow rate. Splitting the flow into two equal size lines versus a single line of the same size will reduce the back pressure on the pump and the required head at a given flow rate.

 

[JoshH]

So what you are really looking for is your TDH or Total Dynamic Head pressure. This is a combination of your Actual head height from the water level in your sump to the top of your return plus the calculated friction loss of your plumbing. The Y fitting will increase your friction loss but not your Head height if that makes sense. An easy way to figure out your friction loss is to use this online calculator....

On-Line Friction Piping Loss

 

[jrlmsla]

Whatever it is called.
will I drastically reduce the flow rate if I have a split loc-line outlet.
Or... for the sake of staying out of the semantics weeds...
80 gallon 48x24x18 frag tank. 1600 gag adjustable dc pump. 3.5 feet up, 3 feet horizontal. 3 90 bends. Split loc-line outlet. YES or NO?

 

[DCR]

Loc-lines are rather restrictive compared to PVC pipe of the same size, but if you use 1" pipe and 3/4" Loc-line and make the split with a 1" PVC tee rather than a 3/4" Loc-line wye, you should get adequate flow from that pump (I would guess about 600-800 gph depending on the head curve of the 1600 gph pump)

 

[Ron Reefman]

Having a split Loc-line (2 nozzles) will not increase the pressure over a single Loc-line outlet nozzle.