Gallons per minute

[bluedog225]

I read somewhere, probably here, that a certain number of gallons per minute was desirable for home water pressure.

Figuring out all the variables for my 1,000 foot run from the meter to the shop would end up with an estimate. I’ve got 1000’ of 5/8” hose run and seem to have good pressure. But good is relative.

I’m going to just measure the flow as is. How many gpm should I be looking for?

Thanks

 

[03ranger]

The formula to calculate GPM thru a pipe is:

GPM=0.0408 X pipe diameter inches (squared) X feet /minute water velocity

 

[micromind]

If you need more flow, set a pressure tank at the shop.

If it's a small tank, the pressure will drop quickly, a larger tank will be slower.

 

[Boilerhouse]

If you are getting 5 gallons a minute, you are probably getting all you need. I measured my lawn sprinkler at 4 gpm, and it is probably the heaviest user of water I have. My pump puts out 10 gpm, and it is way overkill for any fixture or appliance that I have, I got by quite comfortably at my cottage with a pump that put out about 3 gpm.

 

[larry_g]

What you need for a flow rate depends on what you are using the water for. A small rest room in the building is a lot different than watering a large lawn or running a steam cleaner. Figure out what your usage is and then what you need for a water supply. It's just the same as supplying compressed air or electrical power, your loads determine the supply needed.

lg
no neat sig line

 

[Shiftless]

Water pressure in psi, pounds per square inch is different than water flow GPM or gallons per minute. Under certain situations you can have 100 psi static pressure but only flow one gallon per minute flow. Or you could have one pound per square inch static pressure and flow 100 gallons per minute.

1000 ft. of 5/8 tubing is a lot. You probably can’t get over 3-4 gallons per minute at the far end even with a pump capable of 70 psi. With a 30 or 40 psi pump you’re looking at maybe 2 gallons per minute.
If you need more gpm, you’ll likely need to dig up that almost quarter mile of pipe and bury larger diameter tubing.

Another choice of course is accumulating over time lots of water in a tank close to the point of use and then pump out of that when needed.

 

[cvairwerks]

5/8" hose at 1000 feet and standard water pressure is going to give you less than 1 gpm flow...

 

[mike93lx]

The feed to my house is just over 100 psi and I have measured over 25gpm through the hose bibs over a 24 hr period. It's excessive, but we can easily have multiple showers running, while the hose is on.

I recently cut it back to about 55psi on the house side with a prv. I think that pressure works well and we still have good flow. Hose bibs and irrigation are all still on full send and I wouldnt want it any other way.

A single house fixture is going to want about 2 go and 2gpm through a hose will be underwhelming. I'd significantly upsize then regulate down if needed. 5/8 at 1000' is way too little, IMO

 

[Jim greengo]

The feed to my house is just over 100 psi and I have measured over 25gpm through the hose bibs over a 24 hr period. It's excessive, but we can easily have multiple showers running, while the hose is on.

I recently cut it back to about 55psi on the house side with a prv. I think that pressure works well and we still have good flow. Hose bibs and irrigation are all still on full send and I wouldnt want it any other way.

A single house fixture is going to want about 2 go and 2gpm through a hose will be underwhelming. I'd significantly upsize then regulate down if needed. 5/8 at 1000' is way too little, IMO

100 psi is a lot of water pressure for residential water,I would expect you to have problems with pop off valves on water heaters and fill valves on toilets with that kind of pressure.
I'd look in to a regulater myself.

 

[mike93lx]

100 psi is a lot of water pressure for residential water,I would expect you to have problems with pop off valves on water heaters and fill valves on toilets with that kind of pressure.
I'd look in to a regulater myself.

Whole neighborhood is this way and talking to a few neighbors, no one has a regulator (that they know of). Houses are all 20-40 years old, too.

We installed a regulator a few weeks ago and it's working well.

 

[bluedog225]

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

This is through the existing 5/8 hose laying on the ground.

The shop will have a single bathroom, shower, toilet, sink. And a kitchen sink.

With this info, I’m going to commit to a 1” pipe for the water line. With T’s every 200’ for a hose bib. Unless I am missing something

Thanks everyone.

 

[mike93lx]

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

This is through the existing 5/8 hose laying on the ground.

There shop will have a single bathroom, shower, toilet, sink. And a kitchen sink.

With this info, I’m going to commit to a 1” pipe for the water line. With T’s every 200’ for a hose bib. Unless I am missing something

Thanks everyone.

That is much higher than I would have guessed.

I bet you'd be happy with 1" line

 

[firebirdparts]

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

This is through the existing 5/8 hose laying on the ground.

There shop will have a single bathroom, shower, toilet, sink. And a kitchen sink.

With this info, I’m going to commit to a 1” pipe for the water line. With T’s every 200’ for a hose bib. Unless I am missing something

Thanks everyone.

No problem.

 

[Shiftless]

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

This is through the existing 5/8 hose laying on the ground.


Thanks everyone.

Congrats on the great flow!
Wow! I am amazed.
That seems to defy the laws of Physics. (retired Physics teacher here)
We are talking level ground here right? Just for the record, please verify that the water is flowing through one thousand feet of 5/8 inch ID hose and delivering 6 gallons in 53 seconds (which is 6.8 gallons per minute.) What is the static water pressure measured at the source before you turn on the valve?

 

[rancherbill]

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

This is through the existing 5/8 hose laying on the ground.

There shop will have a single bathroom, shower, toilet, sink. And a kitchen sink.

With this info, I’m going to commit to a 1” pipe for the water line. With T’s every 200’ for a hose bib. Unless I am missing something

Thanks everyone.

I think you are over designing. Realistically many rural houses work on less than 5 gpm. Our house by choice is set at about 4gpm. We have a 4 bedroom, 4 shower house and it works for us. Well recovery / sedimentation is an issue always. If you pump too much for too long it is hard on wells.

 

[bluedog225]

Well, there are several complicating variables.

-the first 125’-ish is 1.25 pvc.
-it then transitions to 1” pvc at a 90 degree angle
-next it passes through a 3/4”(?) ball valve
-then to 5/8 old craftsman black rubber hose sections. 50’ and 75’ sections from memory
-maybe ten 5/8 ******* along the run to patch rat/rabbit holes over the years
-then through one shut off valve near the termination but not at the end
-mildly uphill for maybe 300’
-then mildly downhill for 700’

Calculating this is above my ability.

The actual measured flow is [edit] reliable.

The fixtures in the shop will be about 10’ higher than the test elevation.

PS-This is “city” water. No pump.

 

[mm08822]

The 400' of net height surely adds pressure to overcome a lot of the restrictions and this is in addition to the city supply pressure.

Think of a 400' water tower.....now add your piping/hoses onto that output.

 

[bluedog225]

I agree it helps. Though the measurements are horizontal feet, not vertical.

 

[mm08822]

Still a positive delta H.

 

[bluedog225]

Sorry, I don’t have a static pressure measurement.

 

[PoorUB]

I read somewhere, probably here, that a certain number of gallons per minute was desirable for home water pressure.

Figuring out all the variables fit my 1,000 foot run from the meter to the shop would end up with an estimate. I’ve got 1000’ of 5/8” hose run and seem to have good pressure. But good is relative.

I’m going to just measure the flow as is. How many gpm should I be looking for?

Thanks

How much flow you want depends how much flow you need. What are your water uses at the shop? Hand sink, pressure washer? 100 irrigation heads?

I don't think there is a minimum or maximum water flow required. For a hand sink you only need a couple GPM. A pressure washer depends on how large the unit is and it's requirements.

I can get 15-20 GPM out of the hose bid on my house.

 

[closetoreality]

I would start by seeing how long it takes to fill a gallon jug and do the arithmitic to extrapolate that over 60 seconds. That will give you a practical estimate on flow rate. Don't use the cross sectional area of the nozzle. You want a representation of the overall house, so use the pipe of your copper house lines. Your flowrate isn't going to change due to conservation of mass, but your velocity will not be an accurate representation of your system as a whole if you use the nozzle cross sectional area (burnoulli)

Divide that flow rate by the cross sectional area of your house piping to obtain velocity.

In general there are major and minor losses. Minor losses are number of fittings/types and cross sectional area changes. Major losses are predominately the total height change and total run (length) of the system because of friction. These frictional losses are dynamic and change with system velocity.

Minor losses can become higher than major depending on system size relative to number and type of fittings. Fittings have guidelines K values which is a scalar/coefficient that is assigned to each fitting type.

Not going to get into the formulas for all this but wanted to offer some high level context.

You mention that you can only estimate, but based on the infrastructure you described, I don't think having the expectation of anything besides and estimate is the reality here. Not without a proper flow and pressure readings. If you have good GPM then that is all you can ask for. Calculating your GPM is a simple and realistic approach. The complication is if you are not satisfied with your GPM. Then you need to analyze your major and minor losses and eliminate where necessary.

Have a plumber take a look if you do end up with low GPM on a test. I can sit here and spit out theory all day as a mechanical engineer and tell you that you need to dig into major and minor losses....a plumber can simplify the conversation and will know exactly what to change when he sees the setup.

 

[PCustoms]

I would start by seeing how long it takes to fill a gallon jug and do the arithmitic to extrapolate that over 60 seconds.

Does anyone read anymore?

I just did the flow test. Filled a 6 gallon water jug to overflow in 53 seconds.

 

[closetoreality]

Congrats on the great flow!
Wow! I am amazed.
That seems to defy the laws of Physics. (retired Physics teacher here)
We are talking level ground here right? Just for the record, please verify that the water is flowing through one thousand feet of 5/8 inch ID hose and delivering 6 gallons in 53 seconds (which is 6.8 gallons per minute.) What is the static water pressure measured at the source before you turn on the valve?

I don't think enough information is known to make that statement. If the pressure from the municipal mainline is high enough it's going to increase the velocity in his system to maintain flowrate...burnoulli. unless he has a PRV separating his system from the mainline.

 

[larry_g]

I don't think enough information is known to make that statement. If the pressure from the municipal mainline is high enough it's going to increase the velocity in his system to maintain flowrate...burnoulli. unless he has a PRV separating his system from the mainline.

Have you read post #11 ?

 

[Shiftless]

Have you read post #11 ?

Thank you
The only factor I didn’t have when I made my statements was the static pressure. If there was 1000 feet of 5/8 inch ID hose laid out straight on level ground delivering 6.8 gpm it would require something around 200 psi static pressure which I knew wasn’t the case. That would blow up common garden hose.

bluedog has since clarified his situation. With the ups and downs and some much larger diameter pipe, I can fully understand how he gets his 6.8 gpm flow rate. His static city water pressure is probably 75-100 psi.

 

[bluedog225]

Good afternoon.

Been laying on my belly in the mud this morning. Doing a leak test. Had to tighten up a few fittings.

To put a bow on this. I ended up with 1.5” pipe rated at 250 psi and the elusive no pipe restriction hdpe compression fittings.

Tees every 300 feet. And I went ahead and ran the pipe out to 1200 feet to use 4 full rolls.

The flow went from 5 gpm to 5 gallons in 13 seconds.

Works for me.

Thanks all.

 

[PCustoms]

23gpm, I think that will do it.

 

[msharley]

Good afternoon.

Been laying on my belly in the mud this morning. Doing a leak test. Had to tighten up a few fittings.

To put a bow on this. I ended up with 1.5” pipe rated at 250 psi and the elusive no pipe restriction hdpe compression fittings.

Tees every 300 feet. And I went ahead and ran the pipe out to 1200 feet to use 4 full rolls.

The flow went from 5 gpm to 5 gallons in 13 seconds.

Works for me.

Thanks all.

You will be able to water all the circus elephants...when the circus comes to town!

 

[My Old Tools]

When I had to run a 1/2 mile of water line at a slight uphill slope, my plumber told me to bite the bullet and put in a 2" line. I never regretted it. This was on a rural water supply with a 3/4" meter and just barely average pressure, maybe 50 psi.