Water Flow

[Allan Edwards]

If a house has City water at 60 psi flowing through a 1/2 pipe, what is the approx "speed" of the water flowing through that pipe in ft/sec?

[magna111]

http://uk.answers.yahoo.com/question...9125500AASA5YF

[parkwest]

Would depend on whether or not a valve was open and to what degree, I would think.

[tjbnwi]

Gallons per minute is more important to answer your question more than PSI. At 15 gallons per minute, and taking into account friction and elbows, wide open pipe;

About 24.5 feet per second

http://www.1728.org/flowrate.htm

Tom

[David Meiland]

http://uk.answers.yahoo.com/question...9125500AASA5YF

Both numbers given in that link seem quite high to me. 5-10 GPM seems more likely. I bet your looking at about 15 FPS max. If you can actually open the pipe in question and time the output of a specific amount of water, you can get a very close answer

[dgbldr]

If a house has City water at 60 psi flowing through a 1/2 pipe, what is the approx "speed" of the water flowing through that pipe in ft/sec?

There is no answer. Insufficiently defined question.

If the pipe is closed at the end, answer is zero.

If the pipe is open at the end, depends on the pipe length, actual ID, number of elbows, etc.

As already said, if you can measure actual flow (gal/min), then it's a simple conversion to ft/sec.

[Dutchman]

Allan, why do you ask? Are you having issues with lack of water pressure?

Like everyone else said, lots of variables.

[Happy Home]

Allen - curious what psi do you get at the street ? Sixty seems low if it is. We have about 110 - 125 psi here.

[Allan Edwards]

Allan, why do you ask? Are you having issues with lack of water pressure?

Like everyone else said, lots of variables.

I typically use recirculating pumps so fixtures get hot water quickly. I had a homeowner who did not want to pay the $1,500-$2,000 for this, The house has (2) 50 gallon gas fired water heaters, and it is taking 4-1/2 minutes to get hot water to the kitchen sink. So I was just curious that given a certain pressure and copper water line size what is the velocity of water coming out of the heaters. I know there are a lot of variables, just trying to get an approx "speed". It would seem to me that in 4-1/2 minutes water would travel pretty far.

Again, I know there are many variables and factors.

[BeachBoy]

Actually, it depends on the length of the pipe.

[Dick Seibert]

Allan:

It doesn't seem right that the city main is only ½", the minimum lateral here is 5/8" and I've got one home with a 3" and another with a 2½" service. Pressure and volume are two different issues, my homes with large water services have 3 acres of landscaping to maintain.

[Happy Home]

So if all the new kitchen faucets are now low flow ~ 1.6 gpm that's 7.2 gal Look at any mfg spec sheet. I think that's based upon 1/2" copper with the last 30" at 3/8". Its the water appliance not the piping looks like.

[BeachBoy]

Allen, here is the information we would need to know:
- What is the length and size of the hot water pipe(s) from the water heaters to the fixture in question? That will tell us how much water has to be displaced before hot water will get to the fixture.
- What is the make and model of the recirculating pump you are using?
- What is the return circulation pipe size?

Keep in mind that you need to be careful not to oversize the pump. If you do, high water velocity can scrub the natural protective coating from the inside of the (presumably copper) pipe where it encounters a burr or a turn, resulting in pinhole leaks over time.

Here is a trick you may be able to use: Put a motion detector in the room that turns on the pump when someone first enters the room. Or make the pump turn on when the lights are on in the room. Either will start flushing out the cold water, some time before the individual turns on the hot faucet.

If you want something less than 4.5 minutes, replace the recirculating pipe with a larger one,
such as 3/4" or 1", although you could run into pinhole leak problems if your supply line is 1/2".

Don't forget to wire in a temperature sensor in series with the power to the pump so it shuts off once the loop is hot. That will minimize unneeded power usage. Taco has one that goes with their pumps.

You can also put in a manually operated push button that the homeowner can push to start the pump (but they have to remember to push it when they come into the room), or a flow sensor in the water line (in which case they need to turn the hot water on for a second to trigger the switch, 4.5 minutes before then want hot water.) Both seem annoying to me

Or, see why they want hot water. Would one of the little under sink hot water dispensers give them what they want?

[tjbnwi]

Beach,

Allan said this home does not have a recirc system.


Allan,

At the kitchen faucet, accurately measure how much water is delivered in 1 minute. This measurement takes into account everything from the heater to the low flow faucet. Use that number in the calculator I linked. That will give you your true feet per second.

As someone mentioned in 4.5 minutes, that is 7.2 gallons. If the pipes are not insulated there is also thermal loss.

If it is 1.6 gpm, your feet per second is 2.6114

Tom

[dgbldr]

What Tom said.

Copper pipe, uninsulated, low flow faucet, long-ish run? 4.5 minutes is downright reasonable :)