How Does Friction Loss Effect Pump Performance

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How Does Friction Loss Effect Pump Performance

Postby dlamp67 » Fri Aug 03, 2012 3:27 pm

August 3, 2012

Friction loss due to a large amount of piping and/or fittings can effect a pumps performance greatly. You should take this into consideration when replacing a pump in any application. If the application has a large amount of pipe and fittings, then, you have the potential of undersizing the pump and, therefore, possibly burn up the pump motor due to overloading. This post has a PDF attached that will give you a guide in the calculation of friction loss.

In most cases, friction loss is insignificant, but, in larger irrigation applications, as an example, it can make the difference in the pump selection process.

As always, the information contained within our Forum is meant as only a guideline. If you need expert advise, then, please do not hesitate to contact a professional on this Forum.

Friction Loss Charts.pdf
Friction Loss Charts
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Re: How Does Friction Loss Effect Pump Performance

Postby Pumpmd » Tue Mar 07, 2017 4:17 pm

This needs updated on friction loss from different pipes being used...Poly pipe,galvanized pipe,copper pipe,200psi pipe,sch 40,sch 80,sch 120,CPVC, and "Pex" pipe that has the smallest "ID" at of all of them to create problems inside your house or on long runs of pipe.

"The larger the pipe, the less the friction loss, the greater the volume, the better the pressure".
Remember that after you already checked for a worn pump end. Restrictions(house filters, water treatment device, faucets, etc).

When you have low pressure in your house but great pressure before the "house valve", and you already took out the device as you know "water savers" used to save water for people on city water that has higher water pressure than someone on a traditional well system(goodbye water saver aka "flow restrictor"), the problem can be found in the plumber who used too small of plumbing pipes to furnish enough volume without friction loss to supply the need. I see it all the time, especially with 3/4" Pex. The manufactures may call it 3/4", but if you compare 3/4" Pex with 3/4" copper or 3/4" PVC you will find that the bore opening is much smaller in 3/4" Pex and top it off with elbows & tees (which all have a friction loss) you get even more flow restrictions resulting in pressure loss on use. If you took a pressure gauge and read the pressure at the end of line without water use you would find the correct pressure you started with(excluding elevation loss). Then if you run the water at the end of the line and watch the gauge you will see the loss of pressure which is what people see upon use. This could've been saved if some of the money would've been used making sure large enough supply pipes had been used. I always tell people to try to use 1" Pex, but the plumbers don't want to use it, because it is a little more difficult to work with and will use the saying"it will cost to much". You won't find many plumbers agreeing with me, but rest assured, I am right. Three years ago I re plumbed my house with 1" Pex from 3/4" copper. The larger the pipe, the less the friction loss, the greater the volume, the better the pressure. Preach it to the plumbers, they are the ones who don't think about plumbing whole houses with 3/4 Pex and then if they have a well, blame it on the pump system when it is the too small of water lines causing the problem. Again, I see it all the time and try my best to explain to my customers what is the problem. If plumbers would just open their ears to this, it would help in multiple situations, but most of them think that they have a plumber licence and they know it all, end of story. Talk to the true plumber engineers and maybe that can help with the 3/4 Pex problem around the country. Paying for a little larger pipe would be much less expensive than what you have to do because of too little pipes, including the aggravation.

I see alot of Calcium buildup in shower heads and the other faucets around the house that causes problems when they don't have a water softener. I always suggest soaking them in lime-a-way. Water Softener sell if they have the money. RO system as well, but I'm to busy on well work these days to be getting into people's houses all the time, so I recommend a plumber that knows what he is doing to do the work. "Secondary water standards for drinking water" Nothing over 500TDS for drinking water. Everyone mostly likes bottle water to where it's easy to sell a RO system. I also have a great water treatment guy that I use as well.
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