Water head, pressure, pipe diameter

[desertphile]

Please pardon this multiple newsgroup article. I do not know which newsgroup would be the most-correct. I hang out in talk.origins mostly, so I do not know which hard-science venue would be appropreate for my query. Hydrodynamics does not seem to be represented in the newsgroup list as far as I can tell.

I live and work on a cattle ranch. (Moooo!) We have a fresh-water spring on the side of a hill that produces about ten gallons (38 liters) of water per minute. We want to go up the hill and dig a hole and bury a 55-gallon (208 liter) drum as a collection box and pipe the spring water into the top of the drum; we then want to run a pipe from the bottom of the drum and down the hill into a cabin. (There will also be an over-flow fitting at the top of the drum, but that is not part of my query.)

At the cabin we hope to get around 43 PSI, or about 100 head feet, of water pressure. We plan on using pipe with an inner diameter of 1.5 inches or perhaps 1.0 inches. We do not want to use a water meter / pressure regulator.

The hill's decline is about 20 degrees, but I do not know if that is important to know. As far as I know, what is important is the height of the water source above the water demand (the "head").

My query is:

1) how high up the hill should the collecting drum be?

2) is there a danger of too much pressure if the collecting drum is too high up the hill?

3) is a pressure regulator at the cabin necessary?

I shall appreciate any thoughts and opinions on the subject.

DMR

[digitalmaster]

100 feet of elevation will give you 43.31 pounds of pressure. 1 foot = .43 psi just multiply feet of elevation cahng time .43 to get pressure you want

[SJF]

1. 100 feet of elevation difference.

1. No

2. No

I presume you will use the barrel as a reservoir with overflow of the excess water. Pipe size depend on the horizontal distance and the desired rate of flow. This data is missing.

SJF

[desertphile]

Thank you. Is it really that simple? Seems to me even one of our cows could have figured that out.

[John Rumm]

No need for a regulator, the head is unlikely to vary by more than the height of the barrel anyway.

Yup, the angle makes little difference (it does dictate the length of the pipe which will have some influence on flow rate, but not static pressure.

Your 100' sounds about right

In theory, but even double your proposed head would be unlikely to cause serious problems for most pipes / fittings / brassware etc.

Nope - not unless you need to restrict pressure to some appliance not designed to handle it.

[hallerb]

I did this kinda thing for my mom, back in 1976... geez how time flies:(

Anyhow with a similiar drop and using garden hose we were able to run a sprinkler the kind that goes left and right, for a long time.

in my moms case she had a cistern on the hill, for their home.

I tapped the overflow to a old hot water tank so she could water her garden withourt concern about depleting the water for her house. It worked great till my moved back here and got diovorced.

odd how something that long ago applies here today

[Cameron Dorrough]

You didn't say how far up the hill the spring is... If you plan to bury the barrel higher up the hill than the spring, you will most likely have to install a pump to fill the barrel.

If you do need to install a pump, it is probably cheaper and a lot less trouble to install the barrel, pump and a pressure regulator at the cabin itself to save installing several hundred feet of pipe and pump motor cables - and maybe use the excess head pressure to run a turbine supplying power to both the pump and the cabin.

HTH, Cameron:-)

[Jerry Avins]

50 PSI is not too high for domestic plumbing. The pump switch at my country cabin keeps the tank pressure between 30 and 50 psi. (The tank level is approximately floor level.) There is a pressure-relief valve rated at 150 psi to ensure that the tank doesn't burst from overpressure, and the pipes can withstand more than that. PVC schedule 40 pipe is rated at 280 PSI cold, derated to 210 at 90F. (Derate to 72% to allow for water hammer.) Where freezing is possible, you may prefer polyethylene, which withstands somewhat lower pressure but tolerates freezing and better withstands water hammer.

In any case, 1-1/4" pipe will generously supply your cabin from any reasonable distance. My cabin is supplied by a 1" pipe through a 100' run from the tank I mentioned. My suburban house is supplied from the main 125' distant through a 1" pipe, and inside plumbing is 1/2" copper, though 3/4 would be better. "Just do it" would seem to be appropriate.

Jerry

[desertphile]

Thank you. Your answer matched the other reply. Hummm. Why did I not know the answer? 100 feet of head is 100 feet of head, after all. It does not seem it could be that simple.

Yes.

The greatest demand at the cabin will probably be a shower: about 5 gallons a minute at most. Since the hill's incline is about 20 degrees, I can probably use a sine table to find distance. Angle "A" is 20 degrees and side "a" is 100 feet. Makes me wish I finished high school. :-) Horizontal distance at the moment is unknown because I do not know how far away, climbing the hill, will be 100 feet high.

Thank you for your answers. Since the answer to query #2 appears to be "No," then we can err on the side of too high.

[zxcvbob]

You already have your answer -- 100 vertical feet from the cabin will give you 43 PSI static pressure. The pipe size is determined first by your maximum expected draw rate and then by the length. The more gallons per minutes you want, the larger the pipe to avoid too much pressure drop. (sorry, I don't recall the flow rates for different size pipes) Don't forget that there's a 1.25" pipe size.

Bob

[desertphile]

Humm. Thank you for your reply. We plan on burrying the pipe about 24 inches because freezing is a problem. However we will also plumb a fitting to drain the system. The owner of the ranch, bless her heart, wants water in the cabin even in the winter, so we plan on burrying the supply system and then adding drain taps to the shower and sink.

The owner of the ranch suggested 1.5 inch pipe but I said, guessing, that would be "over-kill." However, it also occured to me that bigger is always better. :-) If they can afford the 1.5 inch pipe, I'll install it. I think polyethylene will be used since that is what is used on other parts of the ranch (there is water already going to The Big House and also water going down here in the bunk house where I live).

Your system uses a pump; the cabin where the ranch owners want water does not have any electricity (nearest power line is 22 miles away) so it must all be gravity fed. Elizabeth wants hot water, however, so an on-demand propane heater will probably be used. Since there will be no tanks at the cabin, perhaps we will skip the pressure relief valve.

Thank you for your reply.

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[desertphile]

That is good to know. We want the system burried around 24 to 28 inches below ground to prevent freezing, so a pressure regulator would have to be located inside and a drain tap added to it. Far better to skip the regulator if not needed.

Great. See, my 2 years of high school did finally pay off! :-)

Cool. Perhaps I'll put it 125 feet just to be sure.

That is also good to know. I would hate to put the sourse too high up the hill and have the sink blow up. :-)

The plan is for only a shower and sink. There was going to be a toilet but the ranch owners purchased a composting "dry" toilet (for $1,100! Eeeak! I could eat for six months on that amount of money).

Thank you for your reply.

[desertphile]

Yeah, damn few of us are getting younger as the days fly by. :-)

Hummm. I was thinking of a second tank at the cabin but the demand for water probably will not be that great.

Thank you for the reply--- I have added it to my notes to tell the ranch owners.

[desertphile]

Hi. Thank you for replying to my query.

The spring is quite high up the hill (at the moment I do not know the height), however there is already a pipe from it going down to the ranch. The goal here is to tap into that pipe to fill a buried 55 drum and have the over-flow continue down to the ranch. The bottom of the barrel would then be plumbed to the cabin.

There is no power at the cabin. As for the excess pressure, the amount of work (w=fd) the water could perform at the cabin would be zero: the water flow would be at where the 55 gallon drum is. But I like the idea of getting power out of the water: at the moment the water flows into a fish pond and then is piped down to the river---- all gravity fed.

[desertphile]

Thank you. Unless I can think of any reason other than cost to not suggest the ranch owners buy 1.5 polyethylene hose, that is what I'll suggest: it is the same size and material currently used elsewhere on the ranch.

As for pressure drops, I'll ask the ranch owners what shower head flow rate they plan on installing. Seems to me they could run five gallons a minute and still suffer no pressure drop.

[hallerb]

1.5 DEFINETELY BETTER! Thats what I helped install for my moms main water line. a gazillion years ago, its pretty cheap to.

you might add a solar panel & battery for minimal lighting too.

[Harry K]

But you could use the overflow if it is run through a pipe down to the cabin. That will give you 43 psi and 10gpm to work with. Would supply quite a goodly steady amount of electricity - expensive electricity until the equipment amortizes but...

The only time you would get less than 10gpm flow would be while water is being drawn at the cabin.

Re: pressure regulator. It is absolutely unneccessary unless you go

-way- up the hill to install the collector barrel.

Re: pipe size. You might as well go with the 1.5 in as the difference in cost between that and a smaller size over 100 ft is minimal.

Harry K

[mm]

You could use the water power to run a dynamo to power a windfan. That you could use to blow the wind more to counteract all those windmills that are slowing the wind down.

Remove NOPSAM to email me. Please let me know if you have posted also.

[ben.aust]

Yeah you are right about almost no pressure drop because it will be very small (about 1psi) for 5 gal/min over 1000' or pipe. You could drop the size to 1 1/4 and not notice the difference. 1 1/2" pipe would give you more capacity (in case someone want to have a shower, run a washing machine and flush the toilet simultaneously).

[Jerry Avins]

...

The distance that matters is the length of the pipe. One elbow or globe valve has about as much pressure drop as maybe eight feet of straight pipe. Use 3/4, or, to be generous, 1". (Generous means you won't mind someone flushing the toilet while you're taking a shower.)

Jerry