What size return pipe should I use?

[uncleof6]

Think about it this way. The pump is rated at 1200gph. If you could get more flow with a bigger pipe added on after the 3/4" pump outlet, it would flow 1500gph, heck, add an 1.5" pipe and get 2000gph... why buy a bigger pump, just add a bigger pipe. Sorry, it doesn't work that way.

Weeellllll not to that extent, but yes it actually does work that way. Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics. (fluid dynamics.) What this means is that upsizing the return pipe size will produce less friction loss, and make a higher flow rate achievable, within the pumps limitations. It is common, and recommended, to upsize the return plumbing one size--and that is the reason. 3/4" up to 1", 1" up to 1.25" and so on. Except in the case of the Danner Mag Drive pumps.

To the thread in general:

If you read the instructions, (who would ever do that for just a pump?) for the Mag Drive pumps made by Danner, sizes 9.5 and larger, it states that the minimum inside diameter tubing on the outlet of the pump needs to be 1.5". This allows the pump to perform according to the published flow curve. Anything smaller, and you will not get the flow rate out of these pumps they are capable of.

 

[uncleof6]

Thanks everyone for your helpful comments. I love this community, with everyone being so willing to offer helpful advice.

What is a loc line, and is there any advantage to using such a thing as opposed to simply putting my pvc line directly into the tank?

Loc line = robo fittings (articulating pipe outlets) Not to any significant extent, they simply increase the friction loss in the system, and reduce your flow rate. Directional flow should be provided by power heads, to keep your return flow at its maximum.

By the way, does anyone know of a type of paint I can use to paint my pvc line into the tank black (assuming if I don't switch to a loc line once I find out what that is)? I'm afraid if I use generic paint it will peel as time goes by. Thanks.

Krylon fusion for the pvc pipe. Finally, someone will use it for its intended purpose: Plastic, rather than the back glass of the tank.

 

[Ron Reefman]

Weeellllll not to that extent, but yes it actually does work that way. Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics. (fluid dynamics.) What this means is that upsizing the return pipe size will produce less friction loss, and make a higher flow rate achievable, within the pumps limitations. It is common, and recommended, to upsize the return plumbing one size--and that is the reason. 3/4" up to 1", 1" up to 1.25" and so on. Except in the case of the Danner Mag Drive pumps.

To the thread in general:

If you read the instructions, (who would ever do that for just a pump?) for the Mag Drive pumps made by Danner, sizes 9.5 and larger, it states that the minimum inside diameter tubing on the outlet of the pump needs to be 1.5". This allows the pump to perform according to the published flow curve. Anything smaller, and you will not get the flow rate out of these pumps they are capable of.

Regarding this quote,"Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics." I'll agree the larger pipe decreases friction (by an almost meaningless amount for our purposes). But lower total head pressure is completely wrong. How does the bigger pipe reduce the head pressure? The fact is it doesn't change the head pressure at all (up or down). And higher flow rate? The pump puts out 1200gph and you can't increase what the pump puts out by adding bigger pipe down stream. Especially when you are pumping against a head. That's basic physics.

 

[symon_say]

Regarding this quote,"Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics." I'll agree the larger pipe decreases friction (by an almost meaningless amount for our purposes). But lower total head pressure is completely wrong. How does the bigger pipe reduce the head pressure? The fact is it doesn't change the head pressure at all (up or down). And higher flow rate? The pump puts out 1200gph and you can't increase what the pump puts out by adding bigger pipe down stream. Especially when you are pumping against a head. That's basic physics.

So you're basically saying that same pump with 3/4" and 1.5" pipe can get water to the same height??

 

[stingythingy45]

I honestly have no idea why people think a larger return pipe is going to magically make the GPH go up.
I mean come on,it's resticted at the pump and at the loc line down to 3/4 anyways.
Just go 3/4 and be happy you don't have to reduce 8 times down from 1 1/2.lol

 

[uncleof6]

Regarding this quote,"Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics." I'll agree the larger pipe decreases friction (by an almost meaningless amount for our purposes). But lower total head pressure is completely wrong. How does the bigger pipe reduce the head pressure? The fact is it doesn't change the head pressure at all (up or down). And higher flow rate? The pump puts out 1200gph and you can't increase what the pump puts out by adding bigger pipe down stream. Especially when you are pumping against a head. That's basic physics.

Dynamic head loss (water in motion in a piping system) is a total of static vertical lift (= head pressure) + friction loss--converted to vertical lift (= head pressure.) Frictioon losses, often adding between 1 and 3 foot of additional head loss to a system--applied directly to the flow curve of the pump. It is more significant than anecdotal comments would make it seem, and is an important consideration is designing any pump fed plumbing system. You select a pump based on the total losses of the system--rather than the static lift.

You do not increase what the pump puts out, you allow the pump to flow at a higher flow point in the flow curve--by reducing the total head loss in the system--the pump performs at that lower point on the flow curve. You are over thinking it.

I did reverse calcs on one system just recently, dunno where the thread is--but the total head loss was ~42' with a pump that shuts down at ~ 44'--- could not figure out why there was no flow--with only, IIRC, 14' of static lift--I would think that to be more than "meaningless for our purposes." An increase in pipe size would reduce that friction loss to ~ 1/3 - 1/4 of the original figure.

The case of the Mag drive pumps is more than "meaningless for our purposes" because, even with that little 3/4" outlet, if you don't use 1.5" pipe, the pump will not operate on the flow curve, rather well below it. Just the way it is, some pumps can handle it, some better--some can't.

The matter can be less significant as you state, or more significant than you think. The point is that up sizing the pipe is reasonable, sound, and valid in every single case--simply put: the pump will flow better.

I don't think so. The flow has to past thru a 3/4" outlet at the pump. So 3/4" pipe or 1" pipe doesn't really make any difference. The bigger pipe only reduces the speed the water moves thru the pipe at, it doesn't increase the flow from a pump. The 3/4" restriction at the pump is the limiting factor. If you could remove the 3/4" restriction and have all 1" pipe, yes, you might get more flow.

I assume this is a return from the sump to the DT. Add a valve (ball or gate) on the output side of the pump and if you are using pvc pipe, add unions on either side of the pump so you can remove it when you need to clean it or service it.

Friction loss is based on the size of the pipe and the velocity (speed--along with surface properties of the pipe) of the water moving through that pipe. Lowering the velocity by lowering the flow rate, OR by increasing the pipe size, will reduce the friction loss. In the latter case, the pump will operate at a higher flow point in the flow curve, in the former, friction loss is added to the system by the valve--result lower flow rate due to increase in friction loss in the valve.

 

[Ron Reefman]

So you're basically saying that same pump with 3/4" and 1.5" pipe can get water to the same height??

Absolutely, no question about it. If a pump can push a 10' head, it can do it in a 3/4" pipe, a 1" pipe, a 2" pipe or a 2ft diameter water tank. It makes no difference. The weight of the air pressure and water pressure that is directly vertical from the 3/4" outlet is the same. Anything outside the area directly above the outlet doesn't matter, it's pushing down on the bottom of the container around the outlet. Otherwise, water pressure would vary based on how big the container is rather than ONLY the height.

 

[uncleof6]

So you're basically saying that same pump with 3/4" and 1.5" pipe can get water to the same height??

Perhaps, but the flow rate will be lower in the smaller pipe. Increased friction loss, if the losses in the piping system are sufficient enough, it will not reach the same height, that it would in the larger pipe--without reaching the shutdown head height. It is very clear, and very concise. It is mathematically demonstrable, though non linear--charts are used. It is also physically observable.

 

[FishNFun]

If the "experts" would stop trying to out brainiac the other and just read the manufacturer directions it clearly says "1 1/2" INSIDE DIAMETER IS THE MINIMUM HOSE SIZE THAT SHOULD BE USED FOR MAXIMUM FLOW" for the Mag pumps which is exactly what I said. No one said anything about magically increasing the output of the pump itself (but why let that stop you from going on and on without answering the OP's question). Whatever gets your post count up I guess. :headwally:

 

[symon_say]

Absolutely, no question about it. If a pump can push a 10' head, it can do it in a 3/4" pipe, a 1" pipe, a 2" pipe or a 2ft diameter water tank. It makes no difference. The weight of the air pressure and water pressure that is directly vertical from the 3/4" outlet is the same. Anything outside the area directly above the outlet doesn't matter, it's pushing down on the bottom of the container around the outlet. Otherwise, water pressure would vary based on how big the container is rather than ONLY the height.

This ain't true, the bigger pipe will lower the capacity of the pump for pushing water to the height it is supposed to do, and i speak about this from experience a do buildings for living a when pumps are install we have to put smaller pipes as the height grows to make water get to the apartments with the proper pressure, otherwise water will only drip in the showers and get there how it should, try doing the experiment with some smaller pump and you'll see.

And example of this is when you put your finger in front of a hose this make the exit smaller and increase the velocity of water going out and this make the water travel further, you don't increase flow, you get the same flow but water goes a lot far away.

 

[uncleof6]

If the "experts" would stop trying to out brainiac the other and just read the manufacturer directions it clearly says "1 1/2" INSIDE DIAMETER IS THE MINIMUM HOSE SIZE THAT SHOULD BE USED FOR MAXIMUM FLOW" for the Mag pumps which is exactly what I said. No one said anything about magically increasing the output of the pump itself (but why let that stop you from going on and on without answering the OP's question). Whatever gets your post count up I guess. :headwally:

I am sorry this disturbs you, but the proliferation of inaccurate information, is a greater issue. An inflammatory post does not help.

If you look at my posts, I made several references to the instructions, for the Danner pumps. Starting with the first one.

Weeellllll not to that extent, but yes it actually does work that way. Larger pipe size = less friction loss = lower total head pressure = higher flow rate = basic physics. (fluid dynamics.) What this means is that upsizing the return pipe size will produce less friction loss, and make a higher flow rate achievable, within the pumps limitations. It is common, and recommended, to upsize the return plumbing one size--and that is the reason. 3/4" up to 1", 1" up to 1.25" and so on. Except in the case of the Danner Mag Drive pumps.

To the thread in general:

If you read the instructions, (who would ever do that for just a pump?) for the Mag Drive pumps made by Danner, sizes 9.5 and larger, it states that the minimum inside diameter tubing on the outlet of the pump needs to be 1.5". This allows the pump to perform according to the published flow curve. Anything smaller, and you will not get the flow rate out of these pumps they are capable of.

I have been repeating this for a very long time, in the DIY section.

I realize that technical discussions, can be lengthy at times, however, it is within these discussions, that the why is found, when a practice or recommendation is brought into question.

 

[FishNFun]

Uncleof6 I should have excluded you from the others since you're the only one stating fact - other than myself.

To answer the OP's question about Loc Line, it's a snap together tubing that is flexible/adjustable. I find the biggest benefit of Loc Line is being able to position the outputs near the surface of the water. This helps with keeping the surface moving and it limits the amount of back siphon that can occur during a power outage (or when you turn of the return pump). If you don't use Loc Line make sure that you drill a couple holes in your return pipe (just under the water line) to serve as a siphon break. Here's link where you can order Loc Line. You really don't need the special pliers - the segments will snap together with a bit of pressure. Good luck!

http://www.savko.com/PartList.asp?pgid=5&ptid=20

 

[antjtc]

I am sorry this disturbs you, but the proliferation of inaccurate information, is a greater issue. An inflammatory post does not help.

If you look at my posts, I made several references to the instructions, for the Danner pumps. Starting with the first one.



I have been repeating this for a very long time, in the DIY section.

I realize that technical discussions, can be lengthy at times, however, it is within these discussions, that the why is found, when a practice or recommendation is brought into question.

Can you please give me your thoughts as to whether my 3/4 in herbie drain can keep up with my mag 12 pump if I plumb the return line from my sump w/ 1 1/4 outside diameter pipe? Can I use both my 3/4 in and 1 in as drain lines or is it too difficult to coordinate the flow w/ two drains? With about 5 ft head I think I can expect maybe 600 gph. I'm also worried that my aqueon 90 gal internal overflow can't handle the 600 gph due to the slits on the top not being very big. Thanks.

 

[uncleof6]

Can you please give me your thoughts as to whether my 3/4 in herbie drain can keep up with my mag 12 pump if I plumb the return line from my sump w/ 1 1/4 outside diameter pipe? Can I use both my 3/4 in and 1 in as drain lines or is it too difficult to coordinate the flow w/ two drains? With about 5 ft head I think I can expect maybe 600 gph. I'm also worried that my aqueon 90 gal internal overflow can't handle the 600 gph due to the slits on the top not being very big. Thanks.

I cannot recommend the use of 3/4" pipe for a siphon drain--or any drain line for that matter. The inside diameter is just too small, and too easily plugged up, even short of a catastrophic blockage, simply by growth inside the pipe. 1" minimum for a siphon drain.

In your case, use the 3/4" bulkhead, with 1" pipe above and below the bulkhead for the siphon. Use a 1" dry emergency (no flow in it under normal operating conditions) on the 1" bulkhead. This insures that the dry emergency capacity is greater than that of the siphon. @ 600 gph, you only need the single 1" siphon.

You need to use 1.5" inside diameter, with the Mag 12 pump. Please follow the instructions, that come with the pump, calling for the use of 1.5" pipe.

Am certain the overflow will most likely handle the 600 gph, however, it will not be quiet if for no other reason than the teeth/slots. RR tanks, are not ready for reefs. If you want to effectively double or even triple the capacity of the overflow, cut the slots out.

 

[NEK-ap24]

this thread is scary...Uncleof6 is giving out good information (i.e. correct information) and folks are arguing it but not backing it up with any science. I don't look at it as a battle of brainiacs, this is a matter of correcting misinformation. I think it is fairly wise to be sceptical about what you read in forums without knowing the qualifications of the person presenting the information. But if you don't trust something that is posted, I would suggest that you research it a bit more first. "After" that research come back and respectfully offer your opinion in the forum, don't just fire back as if you were being personnaly attack.
Reef Central has a head loss calculator on the home page; pick any pump you like, add a vertical distance you want to return the water then play with the calculator and change the pipe diameter to see the GPH go up. If you were to research the pump you chose, you will see that you will never exceed the manufacturer's claimed max GPH, but you will get closer to it with larger diameter pipe.

Looking at the OP, with a mag 12, at 5 feet vertical (with no other fittings) the calculator suggests that with .75" pipe he could expect 795 GPH, if he were to use 1.5" pipe he could expect 1010 GPH, I would say that is very significant.

 

[Saltydrip]

NEK-ap24, Thank you for posting that about the calculator. I'll be upsizing my return like this week now!!

 

[antjtc]

I cannot recommend the use of 3/4" pipe for a siphon drain--or any drain line for that matter. The inside diameter is just too small, and too easily plugged up, even short of a catastrophic blockage, simply by growth inside the pipe. 1" minimum for a siphon drain.

In your case, use the 3/4" bulkhead, with 1" pipe above and below the bulkhead for the siphon. Use a 1" dry emergency (no flow in it under normal operating conditions) on the 1" bulkhead. This insures that the dry emergency capacity is greater than that of the siphon. @ 600 gph, you only need the single 1" siphon.

You need to use 1.5" inside diameter, with the Mag 12 pump. Please follow the instructions, that come with the pump, calling for the use of 1.5" pipe.
Thanks for the great advice. I think I will cut the teeth out but I am limited by my three quarter in bulkhead even if I use one in pipe on it. Any thoughts on how else I can get the overflow to handle a higher flow rate if I manage to get my mag 12 at 800gph or higher? Should I add an overflow box?
Am certain the overflow will most likely handle the 600 gph, however, it will not be quiet if for no other reason than the teeth/slots. RR tanks, are not ready for reefs. If you want to effectively double or even triple the capacity of the overflow, cut the slots out.

 

[uncleof6]

I cannot recommend the use of 3/4" pipe for a siphon drain--or any drain line for that matter. The inside diameter is just too small, and too easily plugged up, even short of a catastrophic blockage, simply by growth inside the pipe. 1" minimum for a siphon drain.

In your case, use the 3/4" bulkhead, with 1" pipe above and below the bulkhead for the siphon. Use a 1" dry emergency (no flow in it under normal operating conditions) on the 1" bulkhead. This insures that the dry emergency capacity is greater than that of the siphon. @ 600 gph, you only need the single 1" siphon.

You need to use 1.5" inside diameter, with the Mag 12 pump. Please follow the instructions, that come with the pump, calling for the use of 1.5" pipe.
Thanks for the great advice. I think I will cut the teeth out but I am limited by my three quarter in bulkhead even if I use one in pipe on it. Any thoughts on how else I can get the overflow to handle a higher flow rate if I manage to get my mag 12 at 800gph or higher? Should I add an overflow box?
Am certain the overflow will most likely handle the 600 gph, however, it will not be quiet if for no other reason than the teeth/slots. RR tanks, are not ready for reefs. If you want to effectively double or even triple the capacity of the overflow, cut the slots out.

The 1" pipe, on the 3/4" bulkhead will flow more than you will be able to drag out of the mag 12.

For 800 gph you need ~ 12" of linear overflow without teeth, for 600 gph ~ 9" without teeth. Close enough.

 

[sleepydoc]

+1 All Uncleof6's comments. In most cases, the resistance to flow changes with r^4 (i.e. by doubling the diameter, you have 1/16 the resistance.) This is more pronounced at smaller diameters because a small increase in diameter is a larger relative increase. From the original question, going from 0.75" to 1" would be a 33% increase in the size of the pipe, meaning an almost 70% drop in resistance.

For a given pressure, the water will flow more slowly in the larger pipe (part of the benefit) until it reaches the outlet but the total amount of water will be the same. In the case of a return pump, the total flow will actually increase because of the decreased resistance.

Remember, resistance is a function of diameter and length, so just because you may have a narrow fitting it doesn't mean you can't benefit from a wider length downstream.

 

[mvsjrs]

When in doubt, experiment. I know this is an old thread but the question is important to anyone plumbing a system. Here is what I did.

I have a "trident" coming off a TurboSea 1740 (aka BlueLine 70 HD). It is rated for 1740 gph. The outlet of the pump is 1". The "trident" expands immediately to 1 1/4" plumbing with three 1" outlets. The vertical head is about 6 feet. There are dual 1" siphon overflows to handle the volume.

So...

Filling a 5 gallon bucket (measured accurately) with 1 outlet of 1" tubing gave 15.7s average. That gives 1,147 gph.

Filling the same 5 gallon bucket with 2 outlets of 1" tubing gave 10.0s average. That gives 1,800 gph.

We can debate the "why's" but my fish will be enjoying 653 gph more flow.