Size of Hole for 1 Litre/Minute Flow Rate?

No, there isn't. The flowrate will vary with the drop in head as the pipe empties.

But if the tank of fluid is being replenished at the same rate as you need to empty, then head pressure should remain quite constant me thinks???????

Quite. GA

Good answer Del

Purpose?

How constant the flow you want to be?

As mentioned the rate will be dependant upon the static head If you want the flow to be constant, force it (put a pump of 1LPM to drain the water may be PD Pump if you want it to be really constant)

UD15

Listen to the Cat. Just install a cheap ball valve and throttle it as need be.

I should have said a maximum flow of 1 Litre per minute, its a environmentally related project to drain a lagoon at a set rate. I believe it does not matter if the flow falls below that rate just that it doesn't exceed it.

Also have a project that needs draining at a Litre per second! Any rough ideas on the size hole that would need? Again drop off in rate towards the end isn't a problem just that it doesn't exceed a maximum.

Thank you for your help gentleman.

I make it a 1.97mm dia. orifice at 4m head. I'd have thought 2mm would be near enough.

Cheers...........Codey

I hadn't noticed the other posts where it went to 1 litre/sec. For that flow orifice dia comes to 15.2mm. Coefficient of discharge is close to 0.62.

Cheers.........Codey

GA Del. Good old simple idea

I have to agree with the furry one. I'd use a ball valve to adjust the flow in both cases.

I think debris will be your enemy. A small hole will be more prone to clogging, too.

Thank you sir for your advice.

What is the website available for help?

Ragab - Syria

Thank you sir for your help.

You can help me by sending me PM.

Ragab - Syria

We had already thought of that, drilling the hole in the top and gravity will do the rest and hopefully the sediment in the bottom will stay there.

For a rate of 1 Litre per Second we have calculated a hole of 20mm any further thoughts on this?

And I thought cats didn't like water?

Cheers!

For storage facilities with fixed head of liquid, there are a lot of handbooks which derive a different equations which lead to find the velocity at the end of that system (point 2). One of those systems is that one attached.

And simply we can prove that the velocity at the end of the pipe shall be computed as follows:

......................................

where,

L = Length of pipe (ft)

d = Inside diameter of pipe (ft)

V = Velocity (ft /sec)

g = Gravitational constant (ft/sec²)

f = DARCY-WEISBACH friction loss coefficient [f is a function (Re * e/d)]

K = Entrance or Exit Coefficient

Z = Elevational Head (ft)

• If we considered length of pipe L = 0, the equation shall be:

From which V depends mainly on elevation Z...............

• And by assuming a flowrate Q = 1 Lit/min.

The hole cross-sectional area, A can be calculated as A = Q/V

• And the hole diameter, D can be calculated from simple equaion of area, A = ∏ D² / 4

1) Draining a lagoon would probably involve water less than clean - not easy to maintain flow.

2) Who in the world uses a ball valve for metering - a gate or globe would be better.

Just stick a needle valve on the end of the pipe and adjust accordingly, require more flow ? use a larger valve.

Guaranteed to work save you having to reduce the size of the hole if you overdo it.

Hi

At 34 feet of head and approx 15psi of pressure:

with orifice of 1/16" you will have a 0.45 USG/min Actual rate will be 92-94% percent of this value depending on drill length and shape, and water velocity over the orifice. I have based my calculations with velocity factor of approx 38'/second.

If water are containing any solids you are in trouble at this rate of drain.

Also, these calculations are theoretical and may vary

Hope it helps

Wangito.

@

You put a little tank with a ballcock so it doesn't overflow, at the bottom of your pipe. And you have a tap near the bottom of the tank. Open the tap until you get the 1 liter per minute.

The ballcock gives you constant head in the tank, the tap gives you adjustable constant flow.

If you want more accuracy that that, you can use a half 90 vee notch to measure the flow.

or you can have a rubber tube on the end of your tap. Not quite 1 lpm? Then raise or lower the end of the tube a tiny bit until it is.

All we need to know is how do we make a constant current source out of plumbing.

Bill

Then just use the ballcock method. All items can be bought in a plumbing store.

Thanks for all your help gentlemen,

The draining of the first lagoon at 1 litre per minute unsurprisingly didn't work as the 2mm hole just clogged with crud despite drilling at a location of 3 O'clock. We have asked the environmental agency if we can readdress this, probably take them a few weeks to make there minds up.

We are going to use the tried and tested technique of trial and error for the larger second lagoon. As both people on this forum and myself have suggested holes from 15-20mm we are going to start with a 10mm hole and work are way up. Would also like to thank everyone who suggested piping ideas I shall try to incorporate them to avoid turning the surrounding area into a bog.

Thanks again and Dev the cat I apologise if I caused you stress.

Paul

Del the cat even