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# if i have 52 pounds of pressure, how many gallons per minute should i receive through a 1 inch pipe?

city service is 1 inch, flat ground, and servicing fire sprinklers in a new home.

hopefully someone out there is not as anal as the first responder

### 3 Answers

- MugwumpLv 79 years agoFavorite Answer
Hello,

Sorry you got a pretty standard Bill Russell answer.

Ok, I'm afraid that the problem is very complicated and you do not provide enough data. You need the length of pipe, the number and type of fittings, the final pressure required, the friction factor of the pipe, etc... And then you can come up with an equation that relates the change in pressure to the flow rate.

That being said however, we can give a quick approximation for a max flow rate available for 1" pipe.

Let's assume that you are talking about PVC schedule 40 pressure pipe. The inside diameter is 1.029 inches. The maximum recommended design flow rate for this type of pipe is 10 feet per second, I believe. The friction builds up geometrically, so after this speed, the friction just becomes too much.

So Flow rate = Area of pipe times velocity

Q = A * V

Q = ((pi * d^2)/4) * V

Q = ((pi * (1.029 in)^2)/4 * 10 feet/sec * (1 ft^2 / 144 in^2)

Q = 0.058 ft^3 / sec

Now lets convert to Gallons per minute,

Q = 0.058 ft^3 / sec * (60 sec/min) * (7.5 Gallons/ft^3)

Q = 26 gallons per minute.

This is about the maximum flow rate that the system would be designed for.

Good Luck

Source(s): Certified in Plumbing Design - Anonymous9 years ago
What Raul says is generally true, except there is no velocity limit in fire sprinkler piping, unless the water purveyor has special restrictions in the flow in its pipe, or the local fire department restricts flow by ordinance.

A general statement is that if the water supplied to the meter has a residual pressure (pressure when the maximum demand is flowing) is close to 52 psi, your house is single story and the run from the meter to the riser is 50 feet or less, it is likely that the water supply can satisfy a normal sprinkler system design.

There are things which are more important than the gpm you can get from the 1" service. There is a pressure drop through the meter and its fittings, and then through all the pipe and fittings in the building piping. This drop will depend on the type and size of pipe. Another pressure drop to the highest sprinkler.

The National Fire Protection Association has a standard for the installation of residential fire sprinkler systems. It is their Standard 13D. You can view it for free at their web site, NFPA.org.

If you go forward with the installation, be sure that the design and installation have been approved by your local fire authority. In my state a sprinkler system cannot be a DIY project.

Source(s): Retired fire protection engineer - Raul ZLv 49 years ago
The answer given is correct, but I don't agree with the route used because is assuming a velocity for a 1" pipe as it will be the only possible velocity through that diameter, p.e. not considering, noise or vibration and even wear, you can have velocities twice the value recommended of 10 fps.

We are dealing with flow intended for a sprinkler system, so you may consider a residential sprinkler whose orifice diameter is about 1/8" (NFPA 13R). Under this condition may use the following formula:

Q = k (P)^0.5

I don't have the exact value of k (orifice factor) but I know that is in the range of 2 to 5, use 4

Q= 4 (52)^0.5 = 28.8 gpm