Pipe Flow Capacity?

[Anonymous]

Any have a guide that shows how much flow different size conduits can handle?

I am particulary interested in 1" and 1.5' schedule 40 PVC.

Thanks!

Louey

 

[Anonymous]

http://www.plumbingsupply.com/flowchart.html

 

[Len]

Is this for outlet or inlet? Theoritically, with enough pressure and speed, you can pump an obscenely large amount of water through a 1" pipe

 

[Anonymous]

Waz, all those chart show is head loss.

Len, My new tank is being made with 1.5" drains and 1" returns. One on each end. What I am trying to verify is that the 1.5" drains can handle the flow supplied by the 1" returns?

In my case, Iwaki 100's will be the pumps. So the flow will be 2000 GPH on each side. Will that work?

 

[Anonymous]

Now that I know what you need. A 1.5 dia pipe is about 2.25 times the area of a 1 dia pipe. 1" pips can generally drain 600-700 gph. So using the comparison a 1.5 should be able to drain 1350-1575 gph without isseue. I guessed at 6-8ft of plumbing losses which put the 100 at about 1800 gph. I think it is doable but will be pushing it. I would go with 2 inch if it is not to late or down size the dual pumps to maybe dual 70rt which would give you about 1400 gph from each.

 

[Anonymous]

Check out this drain calculator. http://www.prinsco.com/bypipe.cfm

According to this, if I have the slope angle correct at 100%, an 1.5" pipe can handle 53.9GPM which is 3234 GPH. That is of course using a different kind of pipe than I'll be using.

I wonder if that is right?

Louey

 

[Anonymous]

I looked at the site and think that is for their pipeing priducts.

 

[Anonymous]

It is and they show calculation for two different brands of pipe. They varied by maybe 10%.

Waz wrote:

1" pips can generally drain 600-700 gph

Where did you get this information?

Louey

 

[Anonymous]

That is what I recall being generally accepted from 1" drains on tanks. Personally I think it is a little more, but prefer to be cautious. Never know when a hunk of algae or snail will park in the way. Not to mention I have a 1 inch drain on my 60 running about 700 gph. It does not take much closing of the valve I have in the drain line to cause thing to start backing up.

 

[sediener]

My dual 1" overflows can barely handle a GRI520 that puts out in the neighborhood of 1300-1400 gph after head loss. I piped off about 15% of that flow to my fuge so I don't have to worry so much if a snail obstructs a portion of the overflow.

- steve

 

[npaden]

General rule of thumb is assuming that the drain is working on gravity only without suction or standing water above it. (with 20" of water standing above it a 1.5" diameter pipe can drain 5,000gph)

Also it matters on how much of a drop you are getting. If you are just dropping the water a few inches it isn't going to drain as fast as if you are dropping it back to the basement or something like that.

With that said the consensus for a normal drop from a tank down to a sump is about 700gph for a 1" pipe and about 1,500gph for a 1.5" pipe. Those are generally considered conservative, but there are applications that they actually wouldn't handle that much flow. (minimal drop, no water above the drain).

I think you are better off telling us specifics and then asking what diameter pipe we would recommend.

HTH, Nathan

 

[ChrisRD]

I agree with Nathan. Calculating the actual capacity of a gravity drain is similar in complexity to calculating the actual flow of your return pump after form/friction/head losses. It will vary with the specific plumbing setup. The 1500 GPH rule-of-thumb sounds pretty good for planning purposes.

with 20" of water standing above it a 1.5" diameter pipe can drain 5,000gph

Out of curiosity - where does the 5000 GPH figure come from? I would have expected it to be more like 2000 GPH (using the formulas I work with for sizing draw-down orifices in detention pond outlet structures).

 

[npaden]

I just added 3,500 gph to the original 1,500 gph for the extra pressure of the 20" of water standing above it.

This link does a strict calculation for flow out of an opening - http://www.grow.arizona.edu/water/rateo ... ning.shtml

If you put in 1.5" diameter pipe and 0 height it gives you zero flow. If you put in 20" it gives you 56.8gpm or 3,408gph.

Not exactly scientific on my part adding that to the original 1,500gph estimate but I felt that it wasn't way off base. I also thought that you could have the drop be 10 feet or so and that would for sure get you to 5,000gph! :lol:

Heh. Nathan

 

[ChrisRD]

Interesting - thanks for the link (FWIW, I don't think it's correct to add anything to the flow value generated by the calculator).

The formula shown in the link is not as conservative as what we use for the pond draw-down openings. Not sure which one is really more applicable/correct (I'll have to look into that a bit now :wink: ).

 

[npaden]

FWIW, I don't think it's correct to add anything to the flow value generated by the calculator.

So if there is only 1" of water above the drain then a 1.5" diameter pipe will only drain 12.7gpm or 762gph?

That's not right. It depends on how far the water is dropping from the opening to it's final destination. I think that calculator assumes that the flow is going to be even with the opening.

That's why I'm adding to the calculation.

 

[Anonymous]

Well, I will have an 8' long tank. Drains on each end going though 1.5" Durso's. I will have a 4' long sump centered below the tank. The height of the sump will cause me to do a 90 at the bulkhead on the bottom of the tank. Then the pipe can only drop roughly 6" in the drop to the sump. Then another 90 into the sump. The distance from the tank bulkhead to the sump is 2'.

I do have a spare 1.5" bulkhead in the sump that is above the running level of the water. That could allow for a little steep drop to the sump. Maybe another 6" for a total of 12".

Louey

 

[npaden]

How far is the total drop from where the top of the durso will be in your overflow to the water level of the sump?

 

[Anonymous]

The tank is 25" tall. So an inch or so less than that plus the width of the plywood, styrofoam, the 6" drop to the top of the sump. So roughly 30-31 inches. 36-37 inches if I go to the lower bulkhead in the sump.

Louey

 

[ChrisRD]

So if there is only 1" of water above the drain then a 1.5" diameter pipe will only drain 12.7gpm or 762gph?

Maybe. I'm not sure how the formula holds-up for extreme input values (maybe "extreme" sounds too dramatic, but I think you know what I'm getting at :wink: ).

In the case of our tank plumbing, however, I think we're in agreement that even if there was only 1" of water over the inlet of the drain, the height we need to enter into the formula would be the vertical distance from the top of tank water to the outlet of the drain plumbing (unless the outlet was submerged in the sump water in which case we would use the top of sump water).

It depends on how far the water is dropping from the opening to it's final destination.

I agree, unless it's just dropping from the orifice through the open air in which case the height of that fall would not be contributing to flow through the orifice. In that case (like the tank with a hole in the side as depicted on the site) only the water height inside the vessel and above the opening would be contributing to the orifice flow.

Does that make sense?

 

[ChrisRD]

The tank is 25" tall. So an inch or so less than that plus the width of the plywood, styrofoam, the 6" drop to the top of the sump. So roughly 30-31 inches. 36-37 inches if I go to the lower bulkhead in the sump.

Louey

Using a 30" drop with a 1.5" discharge gives about 4174 GPH with the calculator Nathan linked to, but that does not account for form/friction losses of the drain piping.

Using the same input #s, the formula I use at work (VA Stormwater Management Handbook) gives 2522 GPH which seems more believable to me. Again, that does not account for plumbing losses which will decrease the number.

The actual calculation including losses would be iterative, so either someone needs to write a speadsheet/program to do it or spend a lot of time with a calculator. :wink:

Also, keep in mind that these numbers would assume full-syphon in your Durso pipes - ie. no air entrainment. The air entrainment will reduce the capacity further.

Not sure if any of this helps Louey - sorry.