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A simple physics (plumbing) question

Posted by d56auction (My Page) on
Thu, Apr 18, 13 at 0:05

I'm installing two yard hydrants. I plan to come out of the pump and can either have a single 300' line with a hydrant in the middle and one at the end, or I can have a T fitting about 50 feet from the pump and then have two lines from that point. I plant to use 1" something...pex, pvc, or black pe...for everything.

If I use both hydrants simultaneously, in the first scenario, will the first hydrant rob the second hydrant of water volume or pressure? I'm having trouble wrapping my head around this.

Follow-Up Postings:

RE: A simple physics (plumbing) question

If the hydrants are equidistant from the Tee - then the flow should be the same - what ever the water pressure / volume.

If the hydrants are in parallel from the same pipe - it depends upon the volume of water and the pipe size (pressure drop).

I'm not a plumber - there must be charts.

RE: A simple physics (plumbing) question

Easiest solution is to keep the 2 hydrants off one line but put in a flow restriction before the one nearest the pump. An adustable valve would avoid having to do any calculation. Otherwise, I would narrow the first pipe to 3/4" at the end (cut the water volume in 1/2).

Even if running to a Tee, if you want to split the water evenly, going down a pipe size is common. Reduces maximum flow if only one hydrant open, but if your intent is both always open with even flow then either 1.25" to split with 1" after or 1" to split with 3/4" after. Which is ideal depends on flow rate. Using too big a pipe encourages all to flow to nearest hydrant. Too small and tends to restrict all flow. Note that material matters. 1" PVC has bigger inside dimensions than 1" of other pipe materials like CPVC or PEX.
Flow in Pipe sizes roughly: 1" is double 3/4", 3/4" is double 1/2". This is because flow is proportional to surface area which goes with the square of radius of pipe

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