2

If I put a 3/4" outside faucet on 1/2" indoor water pipe will I have more water pressure?

5
  • Should be less pressure but more flow rate when changing from smaller to bigger pipe. Guessing you are on city/town water, so not much you can do pressure wise. Edit your question to explain water system and if you have a pressure reducing valve.
    – crip659
    Commented Jun 3, 2021 at 14:38
  • Pressure <--> voltage. Flow rate <--> current. So, which do you want? Commented Jun 3, 2021 at 15:16
  • 3
    "This homeowner used this one simple trick and plumbers hate him!"
    – MonkeyZeus
    Commented Jun 3, 2021 at 17:09
  • 1
    @MonkeyZeus yes! I just had that on EE-SE: "Power Companies Hate this One Electricity Saving Trick" because it doesn't work, doesn't save anything, and they get the angry calls...!
    – P2000
    Commented Jun 3, 2021 at 17:27
  • The OP should describe the situation in more detail. What is the location and function of the current 1/2" faucet? Laundry room? Utility sink in garage? Is this a cold water only line? A hot water line? Is this a line that is being used to fill a large mop bucket and you want to fill it faster than your current faucet allows? Commented Jun 3, 2021 at 21:16

3 Answers 3

6

You probably mean "flow" rather than pressure, and no, if there is 1/2 inch pipe leading to the hose location and you just attach a 3/4 inch valve to it you will not increase flow. You'll just spend more money on the installation.

To increase flow to the hose you should run new 3/4 inch pipe from a point very near the water meter and from there all the way to your outside tap location. And then, of course, use a 3/4 inch faucet.

1
  • from a point very near the water meter - the water meter is not really relevant. The new pipe has to run from a larger feeder. If the outdoor 1/2" pipe runs three feet indoors to a 1" feeder then you can just run 3/4" pipe to replace that three foot run from the 1" line - no need to go all the way back to the meter, you just need to go far enough until you find a bigger pipe to take from.
    – J...
    Commented Jun 3, 2021 at 23:14
1

I replaced the worn out 1/2" faucets on our two outside faucets with 3/4" because the valve I wanted was only available in 3/4".

It did NOT increase the flow rate through the 1/2" copper piping nor did I expect it to.

To transition from the 1/2" FIP fitting sweated onto the 1/2" copper tubing (original faucet was 1/2" MIP, new one was 3/4" FIP) I used two short adaptors, on each faucet. This increased the expense, needlessly extended the pipe, and was trouble to get leak fee.

1

Fluid speed is a function of flow divided by cross section. increasing the pipe internal diameter from 0.5in to 0.75 in increases the cross section from 0.1963 square inches to 0.4418 square inches, which reduces the speed to about 44% for the same water flow through the pipe. According to Bernoulli's principle, static pressure increases as fluid speed decreases, so you would see a comparable increase of ~2 1/4 times the pressure, assuming the flow can keep up.

To address some of the concerns in the comments: Take a hose and a hand sprayer, after turning the water on, squeeze the handle slowly and steadily. You will notice that the pressure from the sprayer increases as you squeeze the handle to a point. When the opening is sufficiently large that the flow of water is unrestricted, the pressure of the outbound water will stop increasing. In this particular case, that means that if the 1/2" faucet is restricting the water flow in absolute terms, then 3/4" faucet will result in an increase in pressure at the faucet. If you change out the faucet and the pressure stays the same, it just means that a 1/2" faucet was sufficient to keep from restricting the flow of water.

4
  • 3
    But as Jay pointed out, unless the pipe diameter is increased all the way back to the source, this can't happen. Commented Jun 3, 2021 at 15:17
  • diy.stackexchange.com/a/85814/86936 is another example that perhaps explains the concept better than I did.
    – GOATNine
    Commented Jun 3, 2021 at 15:47
  • 1
    This is a home improvement forum. It's not always necessary to force every question into technical perfection. Sometimes the best result comes from just answering what everyone knows the question to mean. In this case, "pressure" isn't even wrong, it's just being used colloquially in a way that is likely to help other people in future if they have the same question. Also, even if you think this answer is an appropriate one, then the appropriate way to handle it would be in a comment suggesting we move the question to Engineering SE.
    – jay613
    Commented Jun 3, 2021 at 20:13
  • 1
    Mod notice: Please keep comments to the site respectful. See our code of conduct for more details.
    – BMitch
    Commented Jun 7, 2021 at 20:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.