Water Hydraulics?

[tuk50]

I need some engineering help! Setting up a water system in tomato patch. I have a couple of 55gal barrels 2ft off the ground gravity fed through a 3/4in hose connecting them to a pvc 1/2in system. The 5 30ft 1/2in pvc lines are connected at one end with pvc T's and capped at the other 5 ends. The 1st 30ft row to the 5th 30ft row has about a 10in drop over 25ft. Question is where do I drill small holes and where do I drill larger holes to keep some sort of equal pressure in all the lines. Do larger holes need to be at the capped ends of the 30ft lines or at the 5th row, which is the fartherest away from the 3/4in hose supply. I'm sure it is obvious for a hydrologist, but I ain't one. .. LOL..
Also I thought about starting with 1/4in holes every 2in and using progressively smaller bit sizes toward the higher pressure side, is this about the right size holes or should they be smaller.
I have to put so much water on my maters here in the desert that I want to let the water dechlorinate for a day or two prior to irrigating, plus making a weak compost tea each day. 8)

[Worth1]

I don't have a license But I have a lot of knowledge on hydraulics.

What you are thinking is (I'm sorry to say) a little off, let me get my mess picked up and I will be back with you later and I will tell you what you need to do.
What you need to do now is tell me where the line is connected to the barrels, top or bottom.
I would also like to know how much pressure you THINK you have.

Worth

[dcarch]

Holey mackerel! That’s a tough one!

First of all, water pressure in the pipes will vary. “Hydraulic head (water pressure)” or “static head” will go from high to low as water level drops in the tanks. Water flow is directly proportional to pressure, so it will be very difficult to control flow in the pipes if pressure changes.

Assuming the branch pipes are level relative to ground, as long as water pressure is maintained, then water pressure will be equal throughout the pipe from one end to the other (water friction and viscosity should not be too important for a 1/2 pipe 30’ long) , therefore the holes need not vary in size for even flow.

To maintain even water pressure within the pipes, the total flow from all the holes in all the pipes should not be more than the flow from the main pipe from the tanks, otherwise equal pressure inside the pipe cannot be maintained.

In you case, there is one pipe that’s lower at the end by ten inches, therefore the water pressure will be higher at the end of the pipe and more water will come out from the holes.

It will be very difficult to control water flow by varying hole sizes, I would suggest instead, use same size hole but vary the distance between holes. You will need to drill very tiny holes so that you don’t lose water pressure. ¼” is way way too big.

You can try using these micro drill bits:

http://www.harborfreight.com/cpi/cta...emnumber=34640

50 PC.SOLID CARBIDE MICRO BIT GRAB BAG

dcarch

[Worth1]

So dcarch how much water pressure do YOU think he will have at the head end of the pipe?

Worth

[dcarch]

Originally Posted by Worth1

So dcarch how much water pressure do YOU think he will have at the head end of the pipe?
Worth

I guess it would be, when the tank is full, the total weight of the water column which would be 24" + 33" (approximate height of a 55 gallon drum).

I forgot the weight of water . Stop pressuring me

dcarch

[tuk50]

I put the faucets at the bottom of each barrell and the top is not sealed, just gravity with the barrells setting 24in's high on platform. The pressure or flow rate is not as important to me as even distribution over the mater patch. Is 1/8in holes small enough, I was just concerned about plugging up from dust and etc. that will blow into open barrels. I plan on just opening the valve each morning to let the water drain at its leisure while I go on to work. That way each barrel will have time to rid itself of some of the chlorine before I need it. 8)

[tuk50]

So, 5th row 1/8in holes 6in's apart, 4th row 5in's apart, 3rd row 4in's apart etc. ?8)

[Worth1]

Originally Posted by dcarch

I guess it would be, when the tank is full, the total weight of the water column which would be 24" + 33" (approximate height of a 55 gallon drum).

I forgot the weight of water . Stop pressuring me

dcarch

A gallon of water weighs 8 1/3 pounds or 8.33

There are 7.5 gallons of water in 1 cubic foot.
55 gallons of water would weigh around 458.15 pounds and contain I think 7.3 cubic feet.

worth

[dcarch]

Originally Posted by Worth1

A gallon of water weighs 8 1/3 pounds or 8.33

There are 7.5 gallons of water in 1 cubic foot.
55 gallons of water would weigh around 458.15 pounds and contain I think 7.3 cubic feet.
worth

Isn't it true that "55 gallon drum" is a generic name, actually it is 45 gallons?

dcarch

[tuk50]

Well, my son and grandson came over this afternoon and we drilled 50 holes with a #45 drill bit and it worked like a charm. It took 15 minutes to fill the barrel with a hose and it took gravity 40 minutes to drain the barrel. The streams were about 12 inches high the first 2/3 rds of the run then slowed down till nothing left in the barrel. We connected two barrels together with a y on one barrel to run to the pvc. We are going to run a 1/4 in line from the faucet to a water cooler float shut off valve that we will mount on the top of the first barrel so we don't have to stand and fill the barrel each time with a hose. Thanks again guys, I would of had a mess on my hands if I had used the larger size holes, but it seems to be working great. 8)

[Worth1]

Originally Posted by dcarch

Isn't it true that "55 gallon drum" is a generic name, actually it is 45 gallons?

dcarch

dcarch
On the open oil market a barrel of oil is 42 gallons as far a drums go there is a 55 gallon barrel and other sized barrels too. So yes you can get a 55 gallon drum I have seen it stamped right on the barrel.
I have had friends that work in barrel factories, talk about some exciting after work talk.

Tuk50 I am glad we could help.
You are more than welcome.8)

Worth

[bryanccfshr]

I would just install pressure compensating drip emitters designed for gravity fed systems where you want them (they will all emit at the same rate as long as you hav the source high enough and don't kill the pressure with excessive friction loss due to long runs. ) 1/2" poly tubing and emitters are cheap and they take the guesswork out of the job. .

You may find this link very helpful http://www.dripirrigation.com/drip_i...hp?pgv=Gravity

[bryanccfshr]

Also is you have holes in a pipe at different elevations (You said it runs downhill)and a low pressure system the water will not fill the pipe entirely on the uphill side before it drains out of the downhill holes. That is why I recommend an emitter over a simple hole. You may also need to raise the barrell(s) Higher to get optimal pressure.

[tuk50]

thanks bryan, but I've got the pvc and barrels already set up and just trying to decide how many and the size of holes so they won't do what you said and empty from the lower end without filling the top end. I may have to just drill hole every couple of feet and experiment till it works. 8)

[bryanccfshr]

Good luck, I hope you get it to work, just don't strip those reverse gears out until you are certain you have a working system. I love to experiment too. In this case you may not just want to modify the size of the holes but also the radial location of the holes in the pipe. For example, 12 oclock at the farthest downhill position rotating downward toward 4 or 5 ocklock towards the uphill side. This may help with the partially filled pipe.