Calculating gpm

[Chillimau]

I need to install a 1200' to 1300' water line. I have calculated that I could get about 100gpm out of a 3" line with about 65 to 70 psi line pressure. Does this sound right? The meter is a 2" meter so it should get close on the flow. I can't remember what the feet per second was but seems like around 5 or 6. From what I have read it should be below 10 fps.

99% of the time this size of line would be overkill. Just thinking about a little fire protection from a pasture fire. A 3/4" frost proof hydrant will flow about 30 to 35 gpm according to the spec sheet. If we had three or four of these scattered around the house and barn, along with a lawn sprinkler system, maybe we could protect the buildings until help arrived?

On another note, I don't think I would need to worry about water hammer in the service line, the fps would probably be 1 to 2 or less, most of the time. Still would need to protect individual lines in the buildings with hammer arrestors. (statement is somewhat redundant because the hammer shock wave would travel backwards into the service line.)

Anyway, I'm not an engineer, but I'm trying to approach it from that perspective. I haven't found anything on fire protection but, 100 gpm is probably still not enough but probably all I could afford. Maybe just wasting my time thinking about it. I am going to run 2" at a min. I haven't priced the difference yet. That may decide for me.

Thanks

Gary

 

[JATO_RaT]

The price difference is considerable between 2" sch 40 and 3" sch 40. The velocity of the water in the 3" and frictional loses will obviously be minimized. I would go with the 3" for all the trouble of trenching and for 1300' of line, wow, thats gonna definitely call for 3". You could always drop to 2" after the first 1000' since frictional loss will be minimal in 2" for 200' to 300' at maximum gpm. I ran 2" for about 800' and definitely notice the drop after about 40 gpm to my irrigation. Rat...

 

[TWINKLE_TOES]

Gary,

Get yourself a copy of "Handyman in Your Pocket" by Richard Young and Thomas Glover. It has the Hazen/Williams pipe tables and equations for head loss and velocity calculations. Its real handy for a lot of stuff, costs about $7. Or you can click here Head Loss calculator More fun but you don't learn much from it. /w3tcompact/icons/wink.gif

If you run your numbers it don't look to good at 100GPM/w3tcompact/icons/frown.gif
Al

 

[Bird]

What kind of irrigation are you guys doing? And what kind of water bills do you have?/w3tcompact/icons/shocked.gif The water main that we (and about 8 or 10 other homes are on is only a 2" for a half mile. And we have a 3/4" meter and lines from the meter to the house, 3 outside hydrants, and the barn. We're on the very end of that water main and have a little over 80 psi pressure. Of course, we sure couldn't get the gpm you guys are talking about.

Bird

 

[Chillimau]

Bird,

I'm not irrigating. Only planning on irrigating if there is a fire!The fellow before me had planned on running a dairy, so I guess he was going need a lot of water for cleaning and more cleaning. I'm seriously thinking about the aerobic septic system you have and using that for pasture irrigation. Not really enough water from the septic system but we are using about 4,000 gal/month right now, so it should help out.

I'm on rural water and my meter is on one of the main lines, (5" or 6" maybe?) and the meter is only about 1500' from a water tower. Prior fellow had installed a 2" compound meter, so might as well use it. I think it was about a $700 meter!

Twinkle toes,

I looked at that Hazen-Williams formula and didn't quite understand what it was telling me, 39.84 head feet? I have a Machinery Handbook, will dig it out and figure what the psi drop is. Just looking at the chart, which doesn't really fit my sizes, doesn't look too good.

AH I think I just found it. Looks like about a 17 psi drop, if I'm reading right. Not too bad, still have 45-50 psi at the faucet.

Is 100 gpm enough to fight a pasture fire around the house and barn ?

Gotta go back later,...

 

[StanInCalif]

100 gpm is enough to run 2-3 decent nozzles at the same time.

<font color=green>stan</font color=green>

 

[Bird]

Chillimau, I agree; if you have that size meter, might as well use it, but your rural water system is obviously a lot different than ours. We have a base water rate of $18 a month even if you don't use any water, and if a person wants a 1" meter instead of the 3/4", there is not only a higher cost for installation, but the base rate is $45 a month. And I don't think our system even has anyone with a 2" meter.

Bird

 

[john4nh]

Hey just wanted to throw in that on a aerobic septic for a typical home 300gpd system under normal loads only discharges the equilvent of a 1/10 an inch of rain. They are expensive systems and here in Tx require annual inspections and maintence. Meaning more $$$

Just reread your post, I just got a permit to install a 4500gpd sytem for a trailor park Iam building. If your putting 4000gpd down the hole what happens is they require more spray area. In my case something like 160,000sq ft. or around 3acres. So here anyway you still only get the equilvent of a tenth of an inch of rain.. I had thoughts of planting a tree farm type operation in the area and use the spray to help irrigate but I came to, too many obstacles for that.

 

[Bird]

<font color=blue>aerobic septic for a typical home 300gpd</font color=blue>

Mine is rated at 500 gallons per day.

<font color=blue>They are expensive systems</font color=blue>

Mine cost $4,000 (a small septic system two years earlier cost $3,800)

<font color=blue>in Tx require annual inspections and maintence</font color=blue>

Requires a maintenance contract with a licensed installer who inspects it 4 times a year.

<font color=blue>Meaning more $$$</font color=blue>

I pay $200 a year for the maintenance contract. I know a guy who'll do it for $125, but I've stayed with someone I know and trust.

Bird

 

[john4nh]

The code requires a calculation on the amount of capacity(sp) It all depends, do you have water saving fixtures etc. I used 300 for an avg. by no means is that the rule of thumb. If I remember right you have a double wide so that makes sense. They are more expesive no matter how you cut it. We installed conventional systems for years again a average $2500 installed. Two 500 gallon tanks 300' field line. dont get me wrong I like the new aerobic systems but they have pros and cons. No eletricity no workie, same with bad pump compressor etc. The old style if you lost power, hurricane whatever you could still flush your commode with a bucket of water.

The price you pay for your service contract sounds right, It is supposed to be going up because of supply and demand. To service these things you have to go to the manufactors class, so usaully you service what you install. I attended some classes and there is a shortage of licensed installers. Hear that anyone wanting to go into business..

I just bought a fourplex that I would like to convert to an aerobic system, when money allows.

BTW Bird what brand do you have? I attended the clearstream class, nice setup.