Flow Rate to Pressure

Water Power = Pressure x Flow rate

At that flow rate their using fire hose. I would hate be standing under it.

Thank you for your reply

I have mistake copy, CP code showed as (12L/min for shower, pipe should be not less than 15mm).

Best regards

NT

Pressure is a given in the system maintained by whoever is provinding the water as a service. If you just use a shower the pressure drop should be minuscle.

If in doubt measure the pressure. Calculating is something for kids. Real engineers have tools to measure it!

Oh and btw you might have a leak in your system. Oh and pressure is 3.5 bar!

It's easy, using any of the many web sites available.

Try a search for something like "converting flow to pressure".

Or, unscrew shower head, screw on pressure gauge, turn on water supply, read gauge pressure.

If I understand your question correctly you want to know what value of water pressure is required for the shower head to deliver 12L/s?

If so; There are two ways to determine the correct water pressure required.

1. Obtain and read the shower head specifications from the Original Equipment Manufacturer (OEM) that list the pressure required to provide 12L/s of flow through the shower head.

2. Turn the showerhead supply valve to the maximum open position and measure the flow rate utilizing a graduated cylinder and a stop watch or a portable flow meter.

If the flow rate is less than 12L/s you will need to increase the supply pressure then perform another flow rate test.

If the flow rate is greater than 12L/s you will need to decrease the supply pressure.

You may have to repeat this procedure several times before you attain 12L/s.

I would choose option 1 as it is much easier and less costly.

If you are performing flow calculations for a housing development or group of buildings it is necessary to find the sum of all flow rates for all installed devices then utilize standard pressure/flow calculation formulae to determine the supply pressure required to provide total flow rate through the existing pipe.

If you are designing a new water distribution system I would allow at least 40% increased supply pipe diameter to account for future expansion and to offset system dynamic pressure losses. (See pressure & flow loss tables for pipe fittings and devices.)

If the above does not make sense to you I would seek the advice of a reputable, competent mechanical engineering firm.

But I would like to know Pressure for this shower point.

How can i convert from Flow rate to Pressure?

1. YOU CANNOT without knowing a lot more information!!
2. 12L/s That's a lot of water. 190.2 GPM. THAT'S one hell of a shower, it would knock the dirt right off of you (and maybe your skin too)! LOL! So I could fill my tub 4 times a minute to overflowing!
3. 12L/m = 3.17 GPM. More like it!

What is the pressure at your water PRV (Pressure Reducing Valve)? Typically the pressure into a house should not exceed 60 to 75 PSI. If it does, you are risking damage to all of the faucets and valves in your house, having a failure and a flood!

Without knowing the max pressure at the PRV, This is a useless "Homework" exercise!

Have fun with your rubber ducky!

hi nt,

Flow and pressure are not related.

Pressure is generated by resistance to flow.

As stated by others, you need to consult the manual on the shower head, it might give you the information you seek otherwise, as suggested by others it's time to get out a bucket and pressure gauges.

Best of luck,

John.

Not so.

Flow is a direct function of pressure applied and quantity of flow is limited by system dynamics such as pipe diameter, length of conveying system, friction, quantity of fittings, altitude, and any flow restriction that creates a pressure drop or resistance to flow in the system.

You cannot have flow without pressure but you can have pressure without flow.

If pressure is increased in/on a given size of conveying medium such as pipe the flow will increase and decreasing applied pressure will decrease flow.

Increasing pipe diameter will not increase flow rate for the same value of applied pressure unless the existing pipe is undersized for the application.

Better than the prior answer, but still not really correct.

For any restriction (a valve, orifice, or shower head) there is a flow curve (flow rate vs. ΔP). In general, increasing the pressure by a factor of 4 will double the flow rate.

You can measure the flow rate of your shower head with a 5 gallon bucket and a timer. You can measure the water pressure just before the shower head with a guage. If you measure the pressure somewhere else, you will need to account for the change in pressure due to the change in height. (34 feet = 14.7 psi)

You need to apply Bernoulli's Equation. But first, you need to know some very important data beforehand in order to solve the problem.

There is NO direct correlation between pressure and flow. You need to know elevation difference for the closed system, initial supply pressure entering the system, initial supply flow rate entering the system, equivalent length of pipe in which the water flows from the supply to the shower head in order to determine velocity head losses, and the roughness factor of the pipe interior surface.

http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section3/bernoulli.htm

some of what you gents are saying is analogous to saying you cannot determine current from voltage. That would be true. The only piece of information needed to determine this is resistance (to flow or current, you choose).

Pressure is as is voltage in electrical circuit

Flow is as is current in electrical circuit

Resistance to flow, is as electrical resistance.

One has to have two of the legs to get the third one.

Dear friend,

The formula linking Flow Rate, Area and Velocity is Q = A x V where A - Area, V = Velocity and again velocity is linked to the Head by the Equation is V^2 = Sq.Rt of (2 x 9.81 x H)

You have given Q as 12 LPS FOR SHOWER. You fix of area of all the holes in the shower and let it be 1.25 cm Pipe Equialent ares of all the holes in the Shower, this is assumed by me since you have not given the hole size and number of holes in the shower. For 1.25 cm pipe area is (1.25) x (1.25) = 1.4625 cm^2

Therefore the Velocity is (12/1.4625) = 8.25 cm. Therefore the head required is

8.25 = Sq.Rt of(2 x 9.81 x H) OR H = Sq.Rt (V^2/2xg)

Hence H = (8.25)^2/ (2x9.81) = (68.06)/(2x9.81) = 3.86 cm

DHAYANANDHAN.S

Was the 1.25 cm pipe an assumption? OP went back and also corrected himself when he stated that the flow was indeed 12 L/m (not L/s), and that pipe is not to be less than 15mm (~5/8"). If the pipe is 15mm, then one will obtain 1.767 cm², and I could not get 1.4625 cm² at all using your assumption of 12.5mm. What kind of math are you smoking today?

His velocity (in pipe) is thusly (12,000 cm³/min)/(1.77 cm²)/(60 s/min)= 113 cm/sec, or 1.13 m/sec.

H= V²/2g₀, thus H= (113 cm/sec)²/(2*980.665 cm/sec²), H=6.510 cm velocity head, which for water constitutes 637 Pa (not much pressure). This formula is converted to pressure as height of equivalent column of the liquid, with static head being left off the formula as a matter of convenience.

OP never really stated what the nature of the problem exactly was, so we can only hope we are being helpful.

He really is not losing much in the pipe if he follows the code, and the pipe is actually as stated.

Why do you want know that?

I'm going to guess that there is not enough flow in the shower head to have a good shower. If this is so you should test the pressure at the entrance to the building with a gauge. This must not exceed 75 P.S.I. or 500K.Pa. If the pressure IS at this level then the pipeline is too small, too long, too rough inside (rusted). This is known as resistance. See other posts.

If the pressure is less than this you will need a pump. Start a new thread to get ideas on what sort of pump.

Jim

I was sort of wondering the same thing. If your shower doesn't have sufficient flow, you might want to check the shower head for a "water-saver" insert. In their quest to save the planet, companies started putting restrictions in their shower heads so you use less water. Unfortunately, this generally results in a lousy shower. Also, since it takes forever to rinse the soap off, you end up taking a longer shower and probably use the same amount of water anyway. Before investing in a pump, try removing the insert and see if it helps.

Hello Dear

CP 48:2005 showed for shower(Hotel) flow is 12L/m. Pipe should be not less than 15mm. But next page showed as (The water supply pipes shall be sized to give a minimum dynamic pressure of 0.7 bar at the inlie end of the flush valve).

But, however i calculate with 12L/m and 15mm are not get 0.7bar. so I take to help from your group.

now, you said that must not exceed 75 PSI. or 500kPa. This value are about nearly 5 bar. what mean for your pressure? I need the pressure for only shower point.

thank you for your answer

Best regards

NT

A lot of the answer(s) depend on the height of the building (hotel) to which you are referring to nt. The actual boundary conditions is such that the pressure is specified (given) at the flush valve. Pipe supplying the shower (from that point) to the shower head is given at 15mm, and the flow of 12L/m is given. This means the pressure distribution system in the hotel must be the result of booster pumps raising water on a high pressure header to the top floor (and providing pressure for the fire protection system), with pressure regulating valves supplying pressure to the rooms on each floor. In high rise hotels, this is a quite involved situation, possibly involving a series of mechanical booster pumps for different ranges of floors.

A simple check of the internal condition of pipes using a fiber-optic inspection camera may tell you something you need to know: "can my pipe support the range of flow I need?" If the pipe is badly tuberculated (for example), or blocked with other debris, then obvious answer to the question. Measure everything, then once you have it all mapped out, you will know where the troubled areas are, and what to inspect and where to inspect. Then you will know what needs upgrading/re-engineering/replacement.

Don't confuse static pressure with dynamic pressure. The Static pressure must not exceed 75PSI so that things don't break.

The standard calls for the MINIMUM pipe size to be 15mm. It COULD be 150mm for example.

The dynamic pressure needs to be measured at a specified point. Presumably the shower head. To grasp the concept I suggest you do this experiment at home. Use 3 garden hoses joined together and a pressure gauge that can be put into the hose joiner as a type of 'T'. First plug the 'T' into the tap and turn on slowly what is the pressure? What is the flow? ( use a bucket and stopwatch. ) Now repeat with the tap on full. You will see the Dynamic pressure will increase. This is called Delta p. Delta means change. Measure the flow rate. Hint; fill bucket to same level at each step then just use time as the variable. This is Delta t. Remove the 'T' and plug on 1 hose and then fit the 'T' to the end turn on full and fill the bucket whilst timing it. You will see a drop in p and t. Do again after adding a second hose. More drop in p and t and even worse after adding the third hose. These changes are due to change in resistance. Delta r

Now put your finger over the end of the hose and you will see the pressure increase but the flow will decrease. If you could repeat the experiment with a fire hose you will see a marked difference in both pressure and flow. This what the standard is trying to define. The amount of dynamic pressure at a specified flow rate that will give a decent shower. You must fit the pipe SIZE ( over 15mm ) or fit pumps and/or tanks to achieve this. Other posters have given you the formulas to do this.

The type of shower head will also have an effect. A head with just a few small holes is like putting your finger over the end of the hose, the p will increase but the flow will drop. That is why they specified flow and pressure at that flow. You could measure the dynamic pressure before a whole bunch of resistance, like just at the point of entry, and get a high reading. So that is why they should also specify the point of measurement. I have English as a first language but I do not understand this; at the inlie end of the flush valve

Jim