Myth on increasing pipe diameter?

[Aqualund]

You nearly doubled the area going from 2" to 3" pipe.

I know?

 

[mr.maroonsalty]

I know?

I realized my err on my drive today; you more than doubled it: pi in2, to over 7 in2. I bet it's fun working with all that water!

 

[jh2pizza]

Make custom sweeps--- Glue a cap on a short length of PVC. Pack it tight as possible with sand. Glue another cap on that end. Carefully warm it up with a heat gun, and bend it around something with the proper radius. If it kinks, start over with a new piece. Its OK if you need to gradually change radius. But be careful about sudden changes or you'll end up worse than a 90. Cut the caps off and knock/wash the sand out.

I used 2" PVC sweeps for Electrical Conduit for years.

 

[wolfblue]

I used 2" PVC sweeps for Electrical Conduit for years.

Much easier using that if its the right radius. They also make some pretty long water sweeps, not at Lowes or HD. Plumbing stores have them. Lowes here does have some conduit sweeps. I was never sure if it was safe to use conduit pvc though. Must be, thanks.

That is damn near genius.

And thanks to you too man! Might take some practice, but it works. Been 20 years or more, so I'm not sure who or what gave me the idea. But it works.

--John

 

[SGT_York]

Conduit PVC is not rated for potable use so you run the risk of adding toxins, albeit the risk is low, it is there.

 

[stephenhall1987]

This is helpful as well. Do you have a rule of thumb for cleaning out your pipe? Any special brush or tool?

It would be arduous work, but Two Little Fishies makes a magnetic hose cleaner. It's small, so those large pvc pipes may be hard to clean.

http://www.thatpetplace.com/magfox-magnetic-hose-cleaning-brush?gdftrk=gdfV2226_a_7c268_a_7c6967_a_7c253719&ne_ppc_id=1463&ne_key_id=26455469&gclid=CO6w9OyClrsCFTEV7Aod_V4AKg

That being said, you could construct your own with a strong magnet.

 

[Lavoisier]

It would be arduous work, but Two Little Fishies makes a magnetic hose cleaner. It's small, so those large pvc pipes may be hard to clean.

http://www.thatpetplace.com/magfox-magnetic-hose-cleaning-brush?gdftrk=gdfV2226_a_7c268_a_7c6967_a_7c253719&ne_ppc_id=1463&ne_key_id=26455469&gclid=CO6w9OyClrsCFTEV7Aod_V4AKg



That being said, you could construct your own with a strong magnet.

An intriguing idea, thank you.

 

[jda]

I just did an experiment on this... kinda. Switched from an Ampmaster to a Diablo DC 10500 pump. It has a 1.25" outlet. I needed this to go up about 10' in head. With a 1.5" spa flex all the way up 10 feet, then split into a pair of 3/4" megaflows, it would flow about 1000 GPH - equivalent to a mag 12 at 4 feet. If I instantly split the pump output into 3/4" and ran those up the the ten feet, then the output more than doubled - I was able to run 3 extra tanks off of this pump by doing it this way. I used flex line, so no elbows, which can slow stuff down.

Out of curiosity, I hooked a garden hose up to one of the 3/4" outlets and the pump could easily pump more than 30 feet (which is as far as I could go in my 2 story with walkout basement home).

My conclusions were this - in CL and low head situations, larger pipe is way better... I doubt that too many people are confused on this. In high head situations, the weight of the water in the larger tubes is not good and you are better off necking it down to the final diameter as soon as possible... high head pumps can overcome this weight quite easily, at a cost of wattage... whereas at least this medium head pump can overcome the distance if the weight is kept down.

 

[Aqualund]

The weight in the water of large tubes is of no consequence as only the weight above the diameter of the outlet matters.

You can read this thread where I made a complete a-hole out of myself for about 3 days before I finally read the information correctly and realized I was wrong.

In your experiment you tested two different materials with different friction coefficients and got different results. No surprise there. Beyond that, do you hold the garden hose 30 feet vertical?

http://www.reefcentral.com/forums/showthread.php?t=2330317&highlight=friction

In summary, although intuitive, your conclusions are in error.

 

[jda]

I used to think this too. Got out my hydro book from college and saw the equations, but most of those revolved around gravity delivery head pressure, aka water towers, and not overcoming gravity to pump up. I ran a real test that said otherwise, but perhaps it is not the weight. Head pressure from gravity appears to be different than water weight back pressure from a turning turbine. A maxijet can pump water up 20 feet of airline tube, but not even 1/3 of that in 1/2" tube. If not the weight then what is it? It is something.

 

[Aqualund]

There's no mystery force making the experiment result differently. In each case you're using different materials, and by the default the experiment is changed. That's just a start.

Also, different pumps are made for different applications, to see the true effect of diameter on a given flow you need to use the same materials, same pump, and only vary the vertical span. From there you will see the effects of the friction.

Some pumps are designed to overcome this at a sacrifice of head...meaning they can't pump as high...so there are a lot of factors...but when all taken into consideration, the math checks out.

 

[jda]

What is the math? What is the equation? I have never found one, or gotten an answer when I asked, only "it just works" or "it checks out." I would like to know, if you know.

The equation for pumping up would involve at least impeller cavitation that is not present in the gravity-only scenario.

 

[Aqualund]

did you even read the thread I posted?

 

[jda]

Nope. I read it in my email before you edited it.

I will read it.

 

[SGT_York]

There are more variables than the math provided for in your link. Generally increasing the diameter will assist but I have done the experiment with a Mag 7 and can tell you for surety that increasing PVC from 3/4 to 1.5" decreases your flow at 15' of head.

The "weight of the water" still trying to come up with an engineering term certainly affects some pumps more than others. So as a general rule increasing is better unless you are looking at a basement sump in which case check your pump headloss charts for a better idea of what may happen when increasing pipe diameter.

I know and have read the engineering math, but my calculations failed to materialize in actual tests, if you doubt it don't spout the math go and try it.

I've got a panworld 200 lying around I wonder how that high pressure pump would fare???

 

[Aqualund]

I know and have read the engineering math, but my calculations failed to materialize in actual tests, if you doubt it don't spout the math go and try it.

You think I'm not? The entirety of my responses have been from first-hand experience in applying the math to reality and seeing the results...That's what I said in the first place.

Of course there are different variables in each situation, that can make results different from the standard equation...but the equation(s) are built around accounting for differences and applying them with formula transformations etc.

But you cannot sit there and use entirely different materials and pumps in your quest to show a .5" diameter pipe can push more flow than a 1" diameter pipe on different pumps, pumps that arent designed for it, different piping, different elevations etc, because then you're changing too many variables...and of course the math won't fit around the one singular subject of the discussion.

 

[jda]

I talked to my college friend who is a hydro engineer for the Army Corp of Engineers. He said that when pumping water with nearly every kind of impeller that indeed the cavitation is a huge issue, as is loss of pressure in between the housing and the impeller. There is no calculation that you can really use without way more information, but water weight plays a huge role and his advice was to decrease the weight as much as possible once you get to about 2/3 or about 3/4 the rated head height of the pump... below that, less elbows and friction is huge and to upsize the pipe. The weight is indeed a huge factor when you are using power - not when you are using gravity to drain... in a draining scenario, a 1000 square mile at 10 feet of head has the same pressure as one square inch, but the one square inch will quickly deplete.

There is gonna be no one answer to this, whether it be to lose weight or go wide... but cutting down elbows probably works in both.

 

[Aqualund]

as an example:

http://www.johnhearfield.com/Water/Water_in_pipes.htm

The only water weight to consider is the weight of the water in the column directly above the output. Really, the only way to reduce the weight of the water on the impeller is to reduce the length of pipe above the impeller...or reduce the salinity!

There is gonna be no one answer to this, whether it be to lose weight or go wide... but cutting down elbows probably works in both.

Yes actually there is an answer to this, unless you're trying to run a maxi-jet 1200 with 2-inch pipe, you want to read the manual from your pump and see at what diameter pipe they derived their performance curves from and design your system around that diameter as a supply line. Generally, you will find that a majority of them used larger diameter piping that their intake and outputs.

For instance, here is a chart for friction. loss versus length of pipe and height from Reeflo:

http://www.reeflopumps.com/images/tips.pdf

Minimize friction losses by using large diameter pipe. First determine the approximate flow rate you want, and the total length of your pipe. The Friction Loss chart will allow you determine the amount of extra “head pressure” will be added to your system due to the diameter of your piping.
(The size of the pump’s suction and discharge ports does not indicate your proper pipe size.)
Choose a pipe diameter that keeps your friction loss below about five feet per hundred feet of pipe. Even if you have a section of small diameter pipe that you can’t change, as with a through the wall fitting, it is still beneficial to use larger pipe on the majority of the run. It matter how much wide pipe you use.
Friction loss chart- The narrowness of the pipe increases friction loss in a geometric manner.EXAMPLE: At 2700 gph using 1.5” instead of 1” pipe reduces friction loss from 97.75’ per 100’ to 11.73’ per 100’. A big reduction in “head pressure”

You can see on the chart that at 600gph, you can reduce friction by nearly 20 times just by switching from .75 to 1.5 diameter pipe. However, there are some dimensions that the differences really aren't sufficient enough to make a change. Of course this is per 100 feet of plastic pipe...most people do not have this much pipe for their systems...so the numbers would change.

This chart isn't brand or style specific either.

 

[jda]

You are right, there is probably is an answer, but we don't know what it is. If it were as simple as you were saying, then there would be no way that a sequence pump could pump significantly more water through a garden hose at 1' below shutoff than it can with a 2" pipe, but it will, every time.

 

[Aqualund]

We do know what it is. You're minimizing the work of people that have worked this out successfully for years. Garden hose has a different coefficient of friction. That's at least one source of difference in calculation.

By your reasoning, we should all be plumbing our systems with garden hoses.