Return pump to much water

[santis]

Hi I'm my name is Santiago and I am very new to this, but with all your posts and help I'm learning. Well i am doing water test with regular tap water, from my tank to my sump, checking on simulated power failures etc.
One problem I have encountered is that my return pump sends the water up from the sump, faster than the water from the tank goes down to the sump, therfore my display tends to overfill.
I have a mag 7 as areturn pump. And a overflow box.
Can someone tell me how to fix this. how to make my pump send less water?
Thanks

[BLKTANG]

put a ball valve in the return line,& turn it down a hair.

[cdbias2]

Or you can add a larger return box.
Or you can run two return boxes.

[tmz]

Restricting the flow may wear on the pump.

Plumb in a tee with one open line going to your display. Put a ball valve on the other line and run it back to the sump. By adjusting the ball vavle you control the amount of water that goes to the sump and in so doing control how much goes to the display . This technique allows your pump to run without restriction and gives you very good control on the amount of water flowing to your display.

[AZDesertRat]

No No No.
Returning the flow to the sump is the most inefficient thing you can do. Centrifugal pumps only consume the power necessary to do the work that is required of them. Restricting the flow going to the display is the correct way since it reduces total flow and does not hurt the pump in any way shape or form period.
Take a look at a test I did recently. You can see as the head goes up due to restricting the flow, the power consumption and GPH go down. It actually makes some pumps work more efficiently and not the reverse.

Here is an example using a Eheim 1260 that I tested awhile back.
I used a 10 psi pressure gauge, ball valve and 1" residential water meter on the discharge side of the pump and a Kill A Watt meter to monitor power.

Open discharge = 63 watts @782 GPH
1 psi (2.31 feet of head)= 60 watts @ 499 GPH
2 psi (4.6 feet of head) = 54 watts @ 433 GPH
3 psi (7 feet of head) = 50 watts @ 356 GPH
3.5 psi (8 feet of head) = 46 watts @ 300 GPH
4 psi (9.5 feet of head) = 43 watts @ 253 GPH

As you increase the head or discharge pressure you reduce the flow which reduces the amount of work being required of the pump. This is true of all centrifugal pumps but not positive displacement pumps which are not too common in our hobby anyway.

[sjm817]

santis:
[welcome]
AZD is correct. There is nothing wrong with valving back a pump to reduce flow. 100% of us that use a return pump do this on our systems. Reducing flow with plumbing restrictions is no different from reducing flow with a valve. Both are adding head to the pump.

Another thing you can do is swap out the mag7 impeller for a Mag3/5 impeller. This will convert the mag7 to a mag5.

[tmz]

Thnanks for the information AZD.
AZD is correct. There is nothing wrong with valving back a pump to reduce flow. 100% of us that use a return pump do this on our systems.
Well obviously not 100%

[A.VOID]

i just ran into the same thing this week-end. Installed the ball valve tonight and all is good in the world.

[sjm817]

<a href=showthread.php?s=&postid=12116034#post12116034 target=_blank>Originally posted</a> by tmz

Well obviously not 100%

"100% of us that use a return pump do this on our systems. Reducing flow with plumbing restrictions is no different from reducing flow with a valve. Both are adding head to the pump."

I guess the way I posted that may not have been clear. I'll state it differently.

If you have a return pump with plumbing attached to it, you will have a reduction in flow due to head loss 100% of the time. 100% of return pumps are "valved back" due to the plumbing attached to them. Head loss is head loss whether it looks like a valve or not.

[tmz]

<a href=showthread.php?s=&postid=12116075#post12116075 target=_blank>Originally posted</a> by sjm817
"100% of us that use a return pump do this on our systems. Reducing flow with plumbing restrictions is no different from reducing flow with a valve. Both are adding head to the pump."

I guess the way I posted that may not have been clear. I'll state it differently.

If you have a return pump with plumbing attached to it, you will have a reduction in flow due to head loss 100% of the time. 100% of return pumps are "valved back" due to the plumbing attached to them. Head loss is head loss whether it looks like a valve or not. Your meaning is clear. I know I didn't make up the tee thing and read all I could about this before plumbing in my Iwaki 100 a couple of years ago and did install a tee which I don't have to use since all of the flow is used in the three display tanks it feeds. It must have been a misguided popular piece of advice on RC at that time. I would not have echoed it if I didn't use it or believe it to be so based on researcdhing at least to my ability. Any way thanks for clearing it up.

[sjm817]

There is a fair amount of info that is less than accurate around. Forums are a good way to discuss such things. BTW, I happen to run a T off my return. Not to reduce flow, but to feed my fuge. If you are looking to reduce flow, it is best to do just that by dialing back the flow. If you have a use for the flow to go elsewhere, a T is a good option.

[AZDesertRat]

I feed my fuge with a tee off the overflow so I get nutrients in the fuge. Different trains of thought I suppose.

[sjm817]

It depends on what your fuge is. Mine isn't for growing fauna, its a RDSB and macro filter for nutrient export/nitrate reduction. I dont want any raw overflow water sent to it. More of a "final stage" filter.

[tmz]

A follow up question.
I run 3 display tanks off my sump with a total of 6 one inch drains(around 3600gph capacity I guess) feeding a 2 inch main drain to the basement.
The return runs 60ft with 7ft vertical through 2 inch pipe with 5 90s to a manifold and is the distributed to each tank. I get most of the 2000gph the Iwaki puts out because of the size of the pipe and the relatively high pressure of the Iwaki.
I want to get more return(3,000 to 4,000) and I am considering a sequence 5800gph pump. I know that with 2 inch pipe I will get more friction loss with this pump . However, I wan't to be able to control the top end of the flow. Should I install a valve to reduce return ? Since there will be significant head loss already, is there a point where further reduction by dialing back becomes inefficient or harmfull?

[sjm817]

Wow, that is some setup you have there! You could put a valve on the Sequence output to adjust flow, or a valve on each tank to individually adjust flow. I assume you are looking at the Hammerhead. Here are the flow numbers from their site. You can see they show rates up to 24' head.

HAMMERHEAD
HEAD FLOW WATT
FEET GPH DRAW
0 5,800 350
4.0 5,500 360
9.0 4,880 375
14.0 4,200 360
16.8 3,600 345
19.5 3,000 325
24.0 600 265

[tmz]

Thanks, with the friction and vertical loss I'm figuring 14 to 16 feet of head which should be on the money in terms of the drain capacity. The watt numbers make it clear that the more you dial back the less watts you use.

[sjm817]

The Sequence pumps seem to dispute that some. They start low, then increase a little, and go back down again, and generally the power usage is pretty flat until you get to the max head rating where the flow and watts both take a big dive.

[tmz]

I have control vavles for each tank's return at the manifold. I have a control valve at the pump outlet now,mainly for maintainence anti siphon since I don't have a check valve. On the new installation, I will continue to have the manifold controls and will add a tee off and a control vavle on the main return. This way if I do have more flow than needed in the displays I can put it to some use.

[jdieck]

Although in general restricting flow does not damage the pump there is always a limit on how much you watn to restrict it.
All pumps have a point were their efficiency is maximum, running above or below that point the efficiency changes creating more power waste that ultimately ends up in heat.
External magnetic driven pumps use air for cooling as well as internal water circulation. Submerged pumps use surounding water and internal circulation for cooling. If the efficiency is dropped too far that additional heat may reflect in two areas.
a) Aquarium water heat up that could be a problem with some marginally cooled aquariums.
b) higher internal temperature increases propensity to precipitate calcium carbonate inside the pump increasing wear to moving parts.

[tmz]

Thanks, jdieck.Seems like with your comments and the sequence numbers the issue of restriction vs. tee is not as cut a dried as earlier posts would indicate.

[sjm817]

This is true. You dont want to restrict the pump severely, close to the point of shutoff. You shouldn't be using a pump that is so far oversized that to need to shut down most of the flow. Use a pump in the proper range and use a valve to adjust the flow to what you need. The Sequence pumps dont seem to follow the "normal" rules for some reason. Possibly because they are direct drive pumps vs magnetically coupled. They seem to have a rather flat power curve.

[AZDesertRat]

Common sense tells you to stick with a pump somewhere close to where you want to be. Obviously using a Mag 36 for a 55 gallon system is not the right application for the pump. For simplicity lets use Mag pumps as an example.
Like I said above using a Mag 36 where a Mag 9.5 is the correct choice is not advisable. But using a Mag 12 and valving it back is within reason. Same goes if you think a Mag 7 might do the trick, buy a Mag 9.5 and valve it down.
All pumps will have a certain amount of inefficiency built in, power consumption due to friction loss, turbulence within the pump volute, an impeller out of balance either dynamically or hydraulically etc. Obviously a Mag 18 is going to draw more power and create more heat than a Mag 12 pumping the same amount of water.

You have to use common sense and match the pump to the application, but slightly oversizing is forgiving and accepted practice.

This is not an endorsement for Mag pumps as I hate them myself and will not use them except to mix fresh saltwater when I need to raise the temperature a few degrees and don't want to use a heater. The use here was because they have an easy to follow numerical sizing system.
I have a closet full of them that have been pulled out of service due to heat, power and noise issues!

And tmz, the use of a tee is cut and dried. It is an old technology that was used in treatment plants and municipal water systems years and years ago when power was cheap and efficiency was in its infancy. They have since figured out power costs money and its cheaper to deliver all the water you produce rather than bleed it back to a reservoir. They now use pump control valves to add additional head much like we use a ball or gate valve to accomolish the same thing.