return pump pvc size?

[rxinc]

Any benefit/ harm to oversizing a return pumps outlet say a 1.5 in. pvc out of a pump that comes w/ a 1 in. in/out

I have the 1.5 in. pipe/unions/etc. already.

I am pumping from a basement 14 ft. up to the tank, and was thinking about the panworld 150 ps.

[Tang Salad]

This would force the pump to work harder, as it would be pushing a thicker/heavier column of water.

If the pump is very overpowered to being with, it might work. But the fact that you're pushing straight up 14 feet makes me think you'd be better keeping to the pump's original output size.

[mg426]

Mag Drive Pumps tell you to double the output size of the pump to get the Maximum flow.

[RicksReefs]

it's always going to be a benefit to increase pipe diameter coming out of the return side. there is no 'heavier' column of water. increasing pipe size reduces friction loss and allows the water to flow with less turbulence and back pressure.

[Tang Salad]

Originally posted by RicksReefs
it's always going to be a benefit to increase pipe diameter coming out of the return side. there is no 'heavier' column of water. increasing pipe size reduces friction loss and allows the water to flow with less turbulence and back pressure.

I don't quite understand how the total water in a given length of 1.5" pipe is not going to be heavier than in a 1" pipe. The wider pipe has more water, and more water equals more weight.

If he used, say a MUCH larger output pipe, let's say 5", would the same pump still be able to push that up 14 feet? I don't think it could.

[RicksReefs]

if the pump is able to push water up 14 feet, it doesn't matter if you increase pipe size, it will push the same if not more thru a larger pipe. water weight is measured in pounds per square inch. the weight is gravity, the pressure in a 1" pipe is equal to the per square inch pressure of a 5" pipe. reduce the friction loss and you increase the flow.

notice how friction loss gets lower the bigger the pipe gets in this chart

http://www.watergarden.com/catalog/_pumps/friction.html

[johnfaas]

what I do is come right off the pump go to a to a 2" ball to a 2 inch T than go to 2 - 1" returns (keeping it 2" 1"+1" )

[rxinc]

Thanks for the replies and the friction loss calculator - which is now bookmarked for the future.

Does the same principle apply about the pipe from the sump to the return pump then?

i.e. sump... 1.5"pipe... reducer to 1".... into pump... 1" out of pump... "backward" reducer to 1.5"pipe ...up thru floor....split into "Y" or "T"... to 3/4" tank returns.

[kgross]

Yes it does. I always suggest oversizing your pipes to reduce friction loss. Then you don't have to worry about the elbows as much (since there is slower velocity of water so you have a much lower friction loss). As a bad rule of thumb if you upsize your plumbing 2 sizes over what you think you need. IE 1 inch to 1 1/2 you will reduce the friction loss so much that you don't need to consider it in your guestimets of flow, so if your pump will put out 1000 gph at 4 feet of head and you use 1 1/2 pipe you will get very close to 1000 gph at 4 feet of head even with a few elbows or other fittings on the pipe. The weight of the water colum is unimportant other than making sure that your plumbing is supported, because the reducing fittings hold up most of the weight of hte water, not the water coming out of the pump, this is why we look at PSI not total weight, it is the PSI that matters.



On your 3/4 inch tank returns depends on what flow rate you are trying to get, what I always suggest is go one size larger than you think you want, test and then reduce if you need higher velocity of the water coming out of the return.

Kim

[xtrstangx]

Originally posted by johnfaas
what I do is come right off the pump go to a to a 2" ball to a 2 inch T than go to 2 - 1" returns (keeping it 2" 1"+1" )

Good idea, bad math. 1 2" pipe section has MUCH more area than 2 1" pipes.

A=pi(r^2)

So a 2" pipe will have 4pi in^2, where 2 1" pipes will have a total of 2pi in^2.

I recommend double the pump output (unless it is a Dart or similar which are meant to run on 1.5" anyways) and run that size as FAR as you can. Up to the bulkhead or right before you put it into the tank, then reduce it to get the velocity you want (remember velocity and volume are different)

[Tang Salad]

Thanks for pointing me in the right direction guys; there's always something new to learn in this hobby.

But can you humor me with one question? Let's say, for example, I have a small Rio (100gph) powerhead. If I expand the output to a 3 foot wide pipe, are you all saying that this tiny pump will still be able to force an equal/greater amount of water up this gigantic pipe?

We're talking about in a return pump situation, not a closed loop, so head pressure is a factor.

Thanks!

[kgross]

Yes, there will be no friction loss in the large pipe , so if the pump has a 2 foot shutoff it will still pump water up 2 feet in that pipe, and if it has 50 gph at 1 foot, with that large pipe you will have 50 gph coming out of it at 1 foot of height. In this case the head pressure is the only factor, friction loss will be so close to zero, that you could eliminate it completely from your calculations for flow rate from the pump.

You are are trying to find out the flow you will get from a pump there are 2 things to concider, total static head pressure, IE how high the pump has to lift the water, and friction loss or dynamic head pressure. Dynamic head pressure is a lot harder to figure out since it is determined by the velocity of the water in the pipe, the lower the velocity the lower the friction the lower the dynamic head pressure, so by increasing the size of the pipe you decrease the velocity, which decreases the friction , which decreases the dynamic head pressure, once the dynamic head loss is below an inch of head pressure it will not effect the flow a noticible amount.

Just for example, using the head loss calculator here on reefcentral, a mag 7 flowing through 4 verticale feet of pipe with 4 feet of horizontal and 4 elbows (a typical return setup) of 3/4 pipe will flow 391 gph, while the same setup with 1 1/4 pipe will flow 466 gph, that is about 15% more flow just from changing the pipe size.

Kim

[Tang Salad]

Thanks Kim, I think I got it now.