Water Pressure Booster Pump & Tank FAQs

Effect of water pressure on water consumption rate
Darcy Weisbach vs Hazen-Williams Equations for Piping Friction Head Loss

Table: Water Pressure vs GPM vs Water Consumption Rate

Does using a higher pump pressure increase water consumption?

Does consumption of water increase when we use a pressure pump On 2017-05-29 by Latasiddharth @gmail.com

And

Can you let me know how much excess water will be consumed when we use a water pressure booster pump ? On 2017-10-02 by s n naik

by (mod) - Yes, here's a table of % OF water use increase when we boost pressure or change pipe diameter

Lata

In my OPINION, yes, unless we take great care, we will use more water when we convert a gravity-fed water supply system (say from a rooftop water tank) to a water supply system that uses a pressure-pump.

That's because the higher "pressure" provided by the pump will increase the water flow rate in litres per minute or gallons per minute at the building's sinks, showers, tubs. (Flush toilets won't use more water than before, they'll just fill faster).

Even with a pressure booster pump set to a rather low 25 psi you'll see a much greater flow rate at the sink or tub faucet. And if your building water supply is from a low pressure municipal supply the same effects will be seen.

Example of water consumption increase: You'll use 21% more water to wash hands going from 30 to 40 psi!

When washing hands for personal hygiene most sources including the U.S. CDC typically recommend washing your hands with soap and running water continuously for at least 20 seconds.

Actual water pressure at a plumbing fixture and therefore water flow rate in gpm or lpm varies between a low (at the CUT-IN) pressure and a high (at the CUT-OUT) pressure.

But for simplicity we'll pretend to ignore that reallity.

Using the Omni PSM to GPM calculator we found that for a 1/2" water pipe (typical or minimal expected in a home)

at 30 psi delivery pressure and using a cross-sectional area of the pipe of 0.19635 square inches, we're using 29.17 gpm. So in 20 seconds we'd use 9.6 gallons

at just 10 psi more, 40 psi we'd use 12.3 gallons.

That's a 21% increase in water use.

Keeping those parameters the same except increasing the water pressure gives the table I'll show below

Water Consumption for Pipe Sizes & Water System Pressure

Water Consumption vs Water Pressure
Water Pressure PSI	Pipe Diameter	GPM	Gallons of Water Used in 20 seconds	% Used Increase From Previous
30	1/2"	29.2	9.6	-
40	1/2"	37.5	12.3	28%
50	1/2"	44.3	14.6	17%
60	1/2"	50.1	16.5	13%
70	1/2"	55.4	18.3	11%
30	3/4"	65.6	21.6	-
40	3/4"	84.4	27.9	29%
50	3/4"	99.7	32.9	18%
60	3/4"	112.9	37.2	13%
70	3/4"	124.8	41.8	12%
30	1"	116.7	38.5	-
70	1"	221.8	73.1	90%

Notes to the table above

• Using the Omni PSM to GPM calculator 2026/07/21
• Calcualtions are for water use at sea level where the atmospheric pressure at the pipe outlet will be 14.7 psi
• We ignore the effects of constrictions in the water flow such as faucet passages and opening size and faucet aerator
• You can buy back some of the increased water usage by changing faucets and shower heads to low-flow fixtures.
• Notice also the very significant difference in water flow rates when we go to a larger pipe diameter
• Related reports illustrating the effect of pipe size and water pressure on flow rate in GPM or LPM
• US EPA, SEWERS, FORCE MAIN Fact Sheet [PDF] (2000) U.S. Environmental Protection Agency,
FlexPVC, WATER FLOW RATES VS PIPE DIAMETER [PDF] ADAPTED from data provided by FlexPVC, Tel: 1-888-PBC-FLEX, Web: flexpvc.com retrieved 2021/12/22 original source: https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml
• WATER CONSERVATION MEASURES
• WATER SUPPLY PIPE DIAMETER vs FLOW
• WELL FLOW TEST for WATER QUANTITY 
• ZONE VALVE SIZE vs GPM where we point out that a 3/4" diameter pipe is actually twice the size as a 1/2" diameter pipe.

The Darcy-Weisbach equation vs the Hazen-Williams equation for friction head loss in water piping systems

I'm Using William Hazen's equation to determine pressure loss in a 2 inch pipe

Just to clarify, I have 280 ft of 3 inch pipe before the softener, and 1500 ft of 2 inch pipe after the softener.

I work at a metal finishing shop. Supplied water pressure from the city is 48 psi, in a 3 inch line. By the time some process water gets used, the pressure drops before reaching my 30 cubic inch water softener. Pressure drops to approximately 28 psi.

I need 60 psi to lift the resin bed and properly backwash. I am looking at a booster pump that will supply 130 gpm at 85 psi to correct this problem.

When I use William Hazen's equation to determine pressure loss in a 2 inch pipe at 1500 ft, it comes out to be over 100 psi. I know this isn't true. (PVC pipe, schedule 80). Am I using this equation improperly or should I be using a different formula to calculate? On 2017-04-19 by John

by (mod) : how to use the The Darcy-Weisbach equation vs the Hazen-Williams equation to calculate friction head loss in water piping systems

John, the Engineering Toolbox to whom I sometimes turn for greater depth in engineering calculations offers this comment

The Darcy-Weisbach equation with the Moody diagram is considered to be the most accurate model for estimating frictional head loss for a steady pipe flow.

Since the Darcy-Weisbach equation requires iterative calculation an alternative empirical head loss calculation like the Hazen-Williams equation may be preferred: - 2017/04/18 original source http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

The engneers also tell us to add a coefficient to the William Hazen equation for pipe material. - http://www.engineeringtoolbox.com/hazen-williams-coefficients-d_798.html

And they offer a cute little head loss calculator at http://apps.engineeringtoolbox.com/head-loss-water-pipe-a_15.html

You'll see that you need, besides pipe diameter and pressure, pipe length, elbows, etc. Pump output ratings like the one you mention also are lift dependent - though lift may be trivial in your application.

h = 0.2083 (100 / c)1.852 q1.852 / dh4.8655 (1)

where

h = friction head loss in feet of water per 100 feet of pipe (fth20/100 ft pipe)

c = Hazen-Williams roughness constant

q = volume flow (gal/min)

dh = inside hydraulic diameter (inches)

Note that the Hazen-Williams formula is empirical and lacks a theoretical basis. Be aware that the roughness constants are based on "normal" conditions with approximately 1 m/s (3 ft/sec).

Now plugging in your data and using a smoothness coefficient of 140 (typical smooth pipe interior) I got

31.5 (ft H2O/100 ft pipe) head loss

13.6 (psi/100 ft pipe) head loss

473 (ft H2O) head loss

205 (psi) head loss

13.3 (ft/s) velocity

Perhaps the high head loss is a factor of that long run of 1500 feet - that's pretty long for a 2" pipe.