How Much Should I Restrict My Return Pump?

woody189

woody189

Member
Hi,
I have a 46 Gal DT and a 10 Gal Sump. I have a return pump rated 820GPH. There are 6 right angles in my PVC pipe, and about 5 feet of vertical and 5 feet of horizontal piping
I have a ball valve to restrict the flow, but I'm wondering how much to restrict it. I currently have 2 U-tubes in the overflow, and have the Ball valve opened quite a bit. There are microbubbles in my tank. I haven't tried getting rid of them yet, but I'm wondering how much flow is too much from a return pump.
I used to strive to have the ball valve as open as possible while making sure that the overflow can keep up because I figured that would mean I would get the maximum filtration from the sump. However, I read a few threads that say to turn down the ball valve.
What reasons would there be to not have the Ball Valve opened as much possible?
Thanks
I just calculated my GPH's after head loss and its about 380GPH. IDK how accurate that is and I think that's assuming the ball valve is fully open
 
bang guy

bang guy

Moderator
Never restrict the input to a running waterpump. So it's zero restriction on the input side.
On the output side you can almost safely shut it down completely, almost. If it's air cooled you just need a small steady stream going through. For water cooled you need a little bit more to keep it from overheating but not much.
 
woody189

woody189

Member
Quote:
Originally Posted by Bang Guy http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479493
Never restrict the input to a running waterpump. So it's zero restriction on the input side.
On the output side you can almost safely shut it down completely, almost. If it's air cooled you just need a small steady stream going through. For water cooled you need a little bit more to keep it from overheating but not much.
Hey Bang. I wasn't clear. I'm not trying to restrict the input (from DT to overflow to sump). I currently have 2 U-tubes, and can easily remove one if I feel it's flowing too fast.
My question was about the return pump (going from the sump to the DT). I was wondering if I should try and leave my ball joint as open as possible going back into the tank? I never really saw a reason not to, but I read a few threads where people were encouraging others to restrict the flow. I just wasn't sure why. I feel like the more flow back and forth trough the DT and Sump, the better.
The microbubbles I was talking about aren't really that bad BTW.
 
bang guy

bang guy

Moderator
If the microbubbles are caused by cavitation (common) then they should stop if you restrict the pump output a little. This is a good reason to restrict the flow. Other than that, I agree with you, restricting the flow reduces efficiency and more flow is generally better as long as the overflow can handle the volume.
Removing a U tube from your overflow will not reduce the flow rate. The flow rate is 100% determined by the pump output.
 
beaslbob

beaslbob

Well-Known Member
I agree with bang.
Woody: With your system and in general all sump systems you should never have to restrict the return pump. Whatever is being returned to the tank will drain to the sump.
If that is not the case then you actually need to redesign the system so that is the case.
If it is not the case then you are probably looking at some kind of flood in the future.
my .02
 
geridoc

geridoc

Well-Known Member
A common cause of microbubbles in a display is the presence of very small leaks in the plumbing. The rapidly flowing water produces an effect called the Pitot effect, which draws air into toe moving fluid through pin-sized holes. Reducing the flow will reduce the Pitot effect, but then why not just buy a smaller (cheaper) pump? Very carefully examine your plumbing, especially where you have solvent-welded elbows, for the presence of salt creep - this is a sure sign of micro-holes that need to be filled. If the plumbing is new you may find that with time the microbubbles will stop anyway, with no action on your part. This is caused by the formation of a layer of slime on the ******** walls of the piping, and the slime may fill very small holes.
 
woody189

woody189

Member
Quote:
Originally Posted by Bang Guy http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479512
If the microbubbles are caused by cavitation (common) then they should stop if you restrict the pump output a little. This is a good reason to restrict the flow. Other than that, I agree with you, restricting the flow reduces efficiency and more flow is generally better as long as the overflow can handle the volume.
Removing a U tube from your overflow will not reduce the flow rate. The flow rate is 100% determined by the pump output.
I will research cavitation.
I wasn't implying that removing a U tube would reduce the flow rate. I meant that if I had to reduce the return pump output (using the ball valve), I could easily remove one of the U tube if needed. In my prior setup, I had only one U tube when the return pump was restricted more. From my understanding, having too large a U tube or too many can result in loss of suction.
Quote:
Originally Posted by beaslbob http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479515
I agree with bang.
Woody: With your system and in general all sump systems you should never have to restrict the return pump. Whatever is being returned to the tank will drain to the sump.
If that is not the case then you actually need to redesign the system so that is the case.
If it is not the case then you are probably looking at some kind of flood in the future.
my .02
Interesting. I've read quite a few threads that encourage a ball valve. Actually, it's possible that they said to put one in for maintenance and not to restrict the permanently.
I'm not sure there is an "issue" with my system, is there? Everything is functioning smoothly, so I'm not sure where a flood would occur.
My sump can hold a few gallons of water that may be siphoned back from the DT through the return lines. My Overflow has no problem starting back up if the power goes out. From my understanding, those are the 2 main causes of floods.
Either way, I agree that it probably would be optimal to install a larger overflow. That said, I probably won't because I don't think there's any danger.
Quote:
Originally Posted by GeriDoc http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479520
A common cause of microbubbles in a display is the presence of very small leaks in the plumbing. The rapidly flowing water produces an effect called the Pitot effect, which draws air into toe moving fluid through pin-sized holes. Reducing the flow will reduce the Pitot effect, but then why not just buy a smaller (cheaper) pump? Very carefully examine your plumbing, especially where you have solvent-welded elbows, for the presence of salt creep - this is a sure sign of micro-holes that need to be filled. If the plumbing is new you may find that with time the microbubbles will stop anyway, with no action on your part. This is caused by the formation of a layer of slime on the ******** walls of the piping, and the slime may fill very small holes.
Microbubbles aren't really an issue. Most of it was from the skimmer, but it's all good now.
All my PVC is freshly solvent-welded. There aren't any leaks/salt creep that I can see (anymore). I'm not gonna buy a new pump, because my current one is working fine. I understand that restricting the flow can sometimes cause the pump to burn out, but the valve is open quite a bit so I'm not too concerned about that.
Thanks for the help everyone
 
beaslbob

beaslbob

Well-Known Member
Quote:
Originally Posted by woody189 http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479526
...
My sump can hold a few gallons of water that may be siphoned back from the DT through the return lines. My Overflow has no problem starting back up if the power goes out. From my understanding, those are the 2 main causes of floods.
...
They are the two main causes and it sound like you have them under control. (Hopefully the return lines have access to air to break siphon and not otherwise drain the 1/2 the display).
The third cause of floods and the one I forgot is the case where the overflow/drain fails from breaking siphon or blockage. In that case you need to insure the sump runs dry before the display floods. After testing I put a line on the sump and insured I never, never filled the sump above that line.
my .02
 
acrylic51

acrylic51

Active Member
Quote:
Originally Posted by woody189 http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479526
I will research cavitation.
I wasn't implying that removing a U tube would reduce the flow rate. I meant that if I had to reduce the return pump output (using the ball valve), I could easily remove one of the U tube if needed. In my prior setup, I had only one U tube when the return pump was restricted more. From my understanding, having too large a U tube or too many can result in loss of suction.
Interesting. I've read quite a few threads that encourage a ball valve. Actually, it's possible that they said to put one in for maintenance and not to restrict the permanently.
I'm not sure there is an "issue" with my system, is there? Everything is functioning smoothly, so I'm not sure where a flood would occur.
My sump can hold a few gallons of water that may be siphoned back from the DT through the return lines. My Overflow has no problem starting back up if the power goes out. From my understanding, those are the 2 main causes of floods.
Either way, I agree that it probably would be optimal to install a larger overflow. That said, I probably won't because I don't think there's any danger.
Microbubbles aren't really an issue. Most of it was from the skimmer, but it's all good now.
All my PVC is freshly solvent-welded. There aren't any leaks/salt creep that I can see (anymore). I'm not gonna buy a new pump, because my current one is working fine. I understand that restricting the flow can sometimes cause the pump to burn out, but the valve is open quite a bit so I'm not too concerned about that.
Thanks for the help everyone
As your probably aware that statement isn't true......Some pumps performance is actually better with a little restriction on the output side of the pump. As far as burning the pump up prematurely.....if done improperly probably, but if done correctly isn't an issue at all.....
 
woody189

woody189

Member
Quote:
Originally Posted by beaslbob http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479791
They are the two main causes and it sound like you have them under control. (Hopefully the return lines have access to air to break siphon and not otherwise drain the 1/2 the display).
The third cause of floods and the one I forgot is the case where the overflow/drain fails from breaking siphon or blockage. In that case you need to insure the sump runs dry before the display floods. After testing I put a line on the sump and insured I never, never filled the sump above that line.
my .02
I'm okay in terms of water being sucked in from DT to sump. The sump is not overflowing by the time the siphon is broken.
My sump is probably set up differently than yours, but I don't top off my sump past a certain baffle, so I don't worry about that.
I thought I had the overflow U-tubes set up properly, but apparently I did not. When I turn off my return pump, air bubbles form within the U-tubes. When I turn the pump back on, water flows through the U-tubes, but not at a quick enough pace to keep up w/ the return pump. I will need to work on that.
Quote:
Originally Posted by acrylic51 http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3479830
As your probably aware that statement isn't true......Some pumps performance is actually better with a little restriction on the output side of the pump. As far as burning the pump up prematurely.....if done improperly probably, but if done correctly isn't an issue at all.....
I wasn't aware of this. I'm not sure what proper/improper restriction is, but I would assume improper is restricting it too much or all the way (instead of simply turning off the pump). I think my set up is adequate, and I don't think I'm doing any harm. It does makes sense to me that too much restriction may cause the pump to overwork and burn out.
I never thought about it before, but I guess what you said also makes sense. I'm guessing that when you restrict the flow, then the water is forced through with greater pressure and may come out with more force. That's the only way I can think of that perfomrance would be improved.
Thanks again
 
beaslbob

beaslbob

Well-Known Member
Quote:
Originally Posted by woody189 http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3480078
I'm okay in terms of water being sucked in from DT to sump. The sump is not overflowing by the time the siphon is broken.
My sump is probably set up differently than yours, but I don't top off my sump past a certain baffle, so I don't worry about that.
I thought I had the overflow U-tubes set up properly, but apparently I did not. When I turn off my return pump, air bubbles form within the U-tubes. When I turn the pump back on, water flows through the U-tubes, but not at a quick enough pace to keep up w/ the return pump. I will need to work on that.
Good idea using the top of a baffle as a reference.
FWIW my third case above is with the pump running. Should those air bubbles build up and break siphon, then be sure the sump runs dry before the display floods.
Hint hint use a powerhead or the intake on you return pump to suck out the air bubbles at (or just behind) the top of the u tube. I just epoxied an air lin nipple on it then ran an air line to a power head. Not only does that help prevent bubbles while running but it also sucks out the air when power returns.
my .02
 
woody189

woody189

Member
Quote:
Originally Posted by beaslbob http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3480170
Good idea using the top of a baffle as a reference.
FWIW my third case above is with the pump running. Should those air bubbles build up and break siphon, then be sure the sump runs dry before the display floods.
Hint hint use a powerhead or the intake on you return pump to suck out the air bubbles at (or just behind) the top of the u tube. I just epoxied an air lin nipple on it then ran an air line to a power head. Not only does that help prevent bubbles while running but it also sucks out the air when power returns.
my .02
good idea, but how do you attach the tubing to the return pump/powerhead? I'm confused.
 
bang guy

bang guy

Moderator
Most powerheads have a venturi aerator attachment. If the powerhead isn't too deep in the water there is sufficient force to pull air bubbles out of an overflow.
 
beaslbob

beaslbob

Well-Known Member
Quote:
Originally Posted by woody189 http:///t/392052/how-much-should-i-restrict-my-return-pump#post_3480189
good idea, but how do you attach the tubing to the return pump/powerhead? I'm confused.
1) do what bang says.
2) I took a small pvc fitting drilled a hole through it for a rigid air line tube. Drilled a 1/16" hole (actually 2 close together lol) in the airline tube. Then epoxied the airline tube in the pvc with the holes at right angles to the flow in the pvc. then epoxied the pvc to the intake of the powerhead. Not the most efficient for restarts as the intake side of the powerhead is slower then the outlet side (diameter is smaller and flow faster on outlet). But it did suck out the air bubles. Just took a little while for restarts.
Same could be done on the return pump as well.
my .02
 
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