Throttle back pump?

[Travis]

I have a Danner Mag 9.5 pump rated at 950 gph. I know using a gate valve will allow me to throttle back the gph. Looking to have it run at around 600 gph.

 

My question is, would all of that back pressure cause any harm to the pump itself? Thanks.

[disaster999]

first off, after all the plumbing, fittings and how high you need to pump the water, all those pressure head combined would probably yield 600gph

 

i havent personally tried it, but from what others have said, throttling back a pump can help reduce wear and reduce power consumption. but from my personal experience, i have 2 pumps with excessive wear on their shaft and developed an extremely loud rattle by just pumping through my quite restrictive plumbing at that time.

[thegambler26]

I have the exact same pump and use it how you're asking. I have roughly 3 1/2 ft of head and it pumps through a tee and 5 elbows. Even after all this at full speed it pumps out a very strong flow. I'm not sure of the exact volume but its strong. I've been using it with the flow throttled down for around a yr and a half with no noises or adverse effects on the pump.

[Travis]

Thanks guys.

[djfrankn]

first off, after all the plumbing, fittings and how high you need to pump the water, all those pressure head combined would probably yield 600gph

 

i havent personally tried it, but from what others have said, throttling back a pump can help reduce wear and reduce power consumption. but from my personal experience, i have 2 pumps with excessive wear on their shaft and developed an extremely loud rattle by just pumping through my quite restrictive plumbing at that time.

Hey there pal. Just to mention that anytime you restrict the pump in the pressure side of an aquarium pump, regardless the size, it will always consume more power and will heat up itself more. I work with pumps frequently in aquarium and pool business, so I know what I am talking about here. Just my two cents to clarify it.

 

@Travis: why don't you put a "t" after the pressure side of the pump (return) with a valve and divert some of the flow back to the sump? That way you have more room to adjust how much flow you want in your DT.

[Travis]

@Travis: why don't you put a "t" after the pressure side of the pump (return) with a valve and divert some of the flow back to the sump? That way you have more room to adjust how much flow you want in your DT.

Thanks, makes a lot of sense.

[disaster999]

Hey there pal. Just to mention that anytime you restrict the pump in the pressure side of an aquarium pump, regardless the size, it will always consume more power and will heat up itself more. I work with pumps frequently in aquarium and pool business, so I know what I am talking about here. Just my two cents to clarify it.

 

@Travis: why don't you put a "t" after the pressure side of the pump (return) with a valve and divert some of the flow back to the sump? That way you have more room to adjust how much flow you want in your DT.

im sure a lot of members here will disagree with you. magnet drive pumps behave differently than direct drive. if you are in the aquarium and pool business and deal with high output pumps that uses direct drive, then yes, they will run hotter and less efficiently. small aquarium pumps with magnet drive doesnt.

 

also, im not your pal, brah

[Rollermonkey]

The new DC pumps offer variable speeds. I know of three companies marketing what are the exact same pumps inside the box: Reef Octopus, Waveline and Speedwave

 

I give you three guesses which one costs more, and the first two don't count.

[BostonMike7]

@Travis: why don't you put a "t" after the pressure side of the pump (return) with a valve and divert some of the flow back to the sump? That way you have more room to adjust how much flow you want in your DT.

 

That's how I have my setup done. Makes it easy to adjust flow.

[AZDesertRat]

Unfortunately that is wrong, restricting the discharge side of a centrifugal pump REDUCES the power consumption and LESSENS the heat producedand wear on the pump. The pump is doing less work with the additional head placed on it so often is more efficient. This is very misunderstood and often confusing but works the opposite.

 

It is all spelled out in two documents that apply to centrifugal force, power and hydraulics, The Laws of Affinity is one and Bernouli's Theory is the other. A centrifugal pump only draws the power required to do the work at hand, plus a little for electrical and mechanical inefficiencies like and device, so more head or restriction means less water pumped, less power consumed and less heat generated.

 

You do not want to restrict the suction side of the pump though, always the discharge side. This has nothing to do with being magnetically coupled, it applies to all centrifugal pumps, pool, drinking water, industrial or otherwise. A simple test with a valve and a Kill A Watt meter will prove this out.

 

Placing a tee after the pump and sending water back to the sump is not advised. it requires more power since you are pumping water you are not using, created more heat and can actually be harder on the pump. Decades ago this was accepted practice but not today with more efficient pumps, in the pump industry we use control valves to do the throttling or newer VFD variable speed pumps so we conserve energy rather than blowing of excess water and wasted energy.

[jestep]

Unfortunately that is wrong, restricting the discharge side of a centrifugal pump REDUCES the power consumption and LESSENS the heat producedand wear on the pump. The pump is doing less work with the additional head placed on it so often is more efficient. This is very misunderstood and often confusing but works the opposite.

 

It is all spelled out in two documents that apply to centrifugal force, power and hydraulics, The Laws of Affinity is one and Bernouli's Theory is the other. A centrifugal pump only draws the power required to do the work at hand, plus a little for electrical and mechanical inefficiencies like and device, so more head or restriction means less water pumped, less power consumed and less heat generated.

 

You do not want to restrict the suction side of the pump though, always the discharge side. This has nothing to do with being magnetically coupled, it applies to all centrifugal pumps, pool, drinking water, industrial or otherwise. A simple test with a valve and a Kill A Watt meter will prove this out.

 

Placing a tee after the pump and sending water back to the sump is not advised. it requires more power since you are pumping water you are not using, created more heat and can actually be harder on the pump. Decades ago this was accepted practice but not today with more efficient pumps, in the pump industry we use control valves to do the throttling or newer VFD variable speed pumps so we conserve energy rather than blowing of excess water and wasted energy.

 

I was just about to jump in on that. This is basic fluid dynamics, even though you are restricting the flow, the pump is doing less work, and thus is consuming less power.

 

Only point I would argue is that on many pumps, if you are restricting flow well past 50% of rated flow, I've seen back-pressure cause a lot of noise and other issues, unrelated to cavitation. In these cases it's most due to design imperfections where the back-pressure will cause the impeller to bounce against the pump walls because the fixed impeller magnets aren't strong enough or the impeller blade design isn't true so it makes contact with the impeller channel walls.

[Travis]

Sweet, gate valve it is.

[Mojado]

Unfortunately that is wrong, restricting the discharge side of a centrifugal pump REDUCES the power consumption and LESSENS the heat producedand wear on the pump. The pump is doing less work with the additional head placed on it so often is more efficient. This is very misunderstood and often confusing but works the opposite.

 

It is all spelled out in two documents that apply to centrifugal force, power and hydraulics, The Laws of Affinity is one and Bernouli's Theory is the other. A centrifugal pump only draws the power required to do the work at hand, plus a little for electrical and mechanical inefficiencies like and device, so more head or restriction means less water pumped, less power consumed and less heat generated.

 

You do not want to restrict the suction side of the pump though, always the discharge side. This has nothing to do with being magnetically coupled, it applies to all centrifugal pumps, pool, drinking water, industrial or otherwise. A simple test with a valve and a Kill A Watt meter will prove this out.

 

Placing a tee after the pump and sending water back to the sump is not advised. it requires more power since you are pumping water you are not using, created more heat and can actually be harder on the pump. Decades ago this was accepted practice but not today with more efficient pumps, in the pump industry we use control valves to do the throttling or newer VFD variable speed pumps so we conserve energy rather than blowing of excess water and wasted energy.

 

 

I was just about to jump in on that. This is basic fluid dynamics, even though you are restricting the flow, the pump is doing less work, and thus is consuming less power.

 

Only point I would argue is that on many pumps, if you are restricting flow well past 50% of rated flow, I've seen back-pressure cause a lot of noise and other issues, unrelated to cavitation. In these cases it's most due to design imperfections where the back-pressure will cause the impeller to bounce against the pump walls because the fixed impeller magnets aren't strong enough or the impeller blade design isn't true so it makes contact with the impeller channel walls.

 

Ugh, I was jogging (actually resting during a jog) when I read this post and meant to reply to it later. Both you guys beat me. It's like putting your hand over the vacuum cleaner hose. The motor speeds up but is actually sucking less current since it isn't doing any work.

[Mojado]

You do not want to restrict the suction side of the pump though, always the discharge side.

 

My Sicce pump is adjustable. It restricts flow on the suction side of the pump. Forget momentarily that most pumps don't allow you to easily restrict input side and that it is always going to be easier to restrict output side. Aside from that, I don't see why output side restriction is recommended over input side. It's mass in vs mass out, should be the same. Since it is pumping up and the pump is submerged, you aren't going to cavitate it by restricting the input side.

[jestep]

My Sicce pump is adjustable. It restricts flow on the suction side of the pump. Forget momentarily that most pumps don't allow you to easily restrict input side and that it is always going to be easier to restrict output side. Aside from that, I don't see why output side restriction is recommended over input side. It's mass in vs mass out, should be the same. Since it is pumping up and the pump is submerged, you aren't going to cavitate it by restricting the input side.

 

I haven't tested in actuality but everything I've learned is that you can still cavitate with head pressure on the output. But based on how small most aquarium pumps are I've always had my doubts that it's even possible to cavitate one but I've never had issues throttling the output so haven't ever needed to try it.

 

Does the sicce actually have a restrictor in the inlet tube or is it where the case itself has vents that end up being throttled?

[Travis]

My Sicce pump is adjustable. It restricts flow on the suction side of the pump. Forget momentarily that most pumps don't allow you to easily restrict input side and that it is always going to be easier to restrict output side. Aside from that, I don't see why output side restriction is recommended over input side. It's mass in vs mass out, should be the same. Since it is pumping up and the pump is submerged, you aren't going to cavitate it by restricting the input side.

 

In this instance, the pump will actually be used in a closed loop system. Not sure if that will make any difference.

[Mojado]

I haven't tested in actuality but everything I've learned is that you can still cavitate with head pressure on the output. But based on how small most aquarium pumps are I've always had my doubts that it's even possible to cavitate one but I've never had issues throttling the output so haven't ever needed to try it.

 

Does the sicce actually have a restrictor in the inlet tube or is it where the case itself has vents that end up being throttled?

 

It restricts flow into the chamber that makes up the suction side of the pump. It does this by reducing the area of the opening into this chamber . . .much like dampeners into a barbeque pit limit air intake. By turning the knob in the pic, a plastic dampener covers a portion of the inlet. You can turn it to the point where it covers the whole opening.

 

In this instance, the pump will actually be used in a closed loop system. Not sure if that will make any difference.

It is going to be easier to restrict output . . .and your pump will be fine doing it this way. Will you be using an additional overflow to feed the close-loop system?

[AZDesertRat]

When you restrict the suction side of a pump you run the risk of cavitation which not only causes mircobubbles but also destroys the impeller and volute of the pump in time. When you look closely at a pump that has suffered from a restricted intake it looks like it has been pumping sand and eroded the surfaces. It also sounds like you are pumping a box of marbles since the microbubbles actually explode inside the pump volute.

 

Aquarium pumps are inexpensive and operate at very low head so some manufacturers do have a way to restrict the suction side with a shutter mechanism that reduces to surface area of the opening. Still not a good idea hydraulically but not the end of the world at low GPH and low head. In a larger pump such as a pool pump up to a municipal pump you wil never find this arrangement as it would quickly destroy the pump.

[Mojado]

When you restrict the suction side of a pump you run the risk of cavitation which not only causes mircobubbles but also destroys the impeller and volute of the pump in time. When you look closely at a pump that has suffered from a restricted intake it looks like it has been pumping sand and eroded the surfaces. It also sounds like you are pumping a box of marbles since the microbubbles actually explode inside the pump volute.

 

Aquarium pumps are inexpensive and operate at very low head so some manufacturers do have a way to restrict the suction side with a shutter mechanism that reduces to surface area of the opening. Still not a good idea hydraulically but not the end of the world at low GPH and low head. In a larger pump such as a pool pump up to a municipal pump you wil never find this arrangement as it would quickly destroy the pump.

Yeah, I can see that risk for a larger system, but for a small (low head, low GPH) submersed pump, that risk isn't there. I've heard that sound you described when a floating bag (I was acclimating) got loose from it's clip and blocked my overflow. I heard the noise and noticed I was shooting bubbles out of my return nozzles. The level in my DT had gone up, the level in my return section of the sump had dropped and I was cavitating my pump. Ugly sound!

[AZDesertRat]

If any of you have swimming pools, try valving the suction side of the pump down and you will hear exactly what I am talking about. The pool pump is the same design as an aquarium pump but larger.

[Mojado]

If any of you have swimming pools, try valving the suction side of the pump down and you will hear exactly what I am talking about. The pool pump is the same design as an aquarium pump but larger.

Is this because the pump for a pool is inline and above ground (above the water line of a pool). It would seem it is easier to caviate at that point.

[AZDesertRat]

No, it is the centrifugal design of the pump and sounds the same even on a drinking water distribution system booster pump with an elevated storage tank feeding it with net positive suction head. What you hear is the bubbles exploding in the eye of the impeller where a partial vacuum is pulled from slinging the water to the outside of the volute and creating a void. Many pool pumps are partially self priming low head design but still operate using centrifugal force.

[Travis]

It is going to be easier to restrict output . . .and your pump will be fine doing it this way. Will you be using an additional overflow to feed the close-loop system?

The pump will be fed from a bulkhead on the main tank. Center/center on the back of the main tank.

[AZDesertRat]

In a closed loop with the suction in the back center you should have no problem running it wide open. If the returns are sufficient size with few restrictions it will have almost 0 headloss since the elevation of the water on the suction side and the outlets are almost the same.

 

I ran an Oceanrunner 3500 in a drilled closed loop with the suction exact back center and the outlets in the upper back corners for 7 years before abandoning it for more efficient propeller type powerheads, first Seios, followed by modded MJ's, then Koralias, followed by Sicce Voyagers, then Hydor Evolutions and now Jebao WP's. The OR 3500 drew 58 measured watts and moved between 900 and 1000 GPH, the Evolutions 1400's drew a measured 5 watts and moved 1400 GPH each so 2800 GPH at 10 watts vs 900 GPH at 58 watts.

I moved the sump returns to the two back drilled holes the closed loop used via the Oceans Motions Squirt so still had the random flows plus the powerheads on a RKL controller so more movement all around for 48 less watts 24/7/365.

[djfrankn]

Unfortunately that is wrong, restricting the discharge side of a centrifugal pump REDUCES the power consumption and LESSENS the heat producedand wear on the pump. The pump is doing less work with the additional head placed on it so often is more efficient. This is very misunderstood and often confusing but works the opposite.

 

It is all spelled out in two documents that apply to centrifugal force, power and hydraulics, The Laws of Affinity is one and Bernouli's Theory is the other. A centrifugal pump only draws the power required to do the work at hand, plus a little for electrical and mechanical inefficiencies like and device, so more head or restriction means less water pumped, less power consumed and less heat generated.

 

You do not want to restrict the suction side of the pump though, always the discharge side. This has nothing to do with being magnetically coupled, it applies to all centrifugal pumps, pool, drinking water, industrial or otherwise. A simple test with a valve and a Kill A Watt meter will prove this out.

 

Placing a tee after the pump and sending water back to the sump is not advised. it requires more power since you are pumping water you are not using, created more heat and can actually be harder on the pump. Decades ago this was accepted practice but not today with more efficient pumps, in the pump industry we use control valves to do the throttling or newer VFD variable speed pumps so we conserve energy rather than blowing of excess water and wasted energy.

Thinking of the explanation given by you it makes sense and something else that you posted after too. Restricting te suction side is detrimental while the pressure side may not be at all. Anytime I have to replace a motor/pump for a warranty call it happened that somehow the pump is constantly cavitating due to a bad plumbing design or valve/pipe restriction. Thanks for the explanation.