Are ball valves ok to use on return lines?

[PirateLove]

I just bought a used Mag 7 (700gph) for my 40 gallon breeder tank for a return pump. When I turned it on, after a few min the water was almost to the top of my return slits and I was getting nervous. Should install a ball valve or buy a weaker pump? I understand it is hard for users on RC to judge what kind of pump people need for their different tanks but I thought I would ask for an opinion. Thanks. :uhoh3:

 

[elFloyd]

I ball valve on the output of the pump is ok. But not on the input to the pump.

 

[lespaul339]

Yes, you can put a ball valve on your return lines.

 

[sde1500]

I run one on my return line, though in hindsight I really wish I got a gate valve, easier to get adjust.

 

[mcgyvr]

yes as stated its always ok to throttle back the output of a centrifugal pump but NEVER do the input as it may start to cavitate and that can destroy the pump,etc..

And yes a gate valve is more "precise" and easier to adjust vs a ball valve but for this application it really doesn't matter..

Some light reading...
https://en.wikipedia.org/wiki/Cavitation

 

[Wazzel]

Ball valve is fine on the output side of the pump.

 

[Shivsreef]

Ball valves are OK on the output of the pump but they are mainly for on/off functions. Like others said above gate valves are much better and give your more control over the actual output.

 

[1jwampler]

Pump will last longer and use less energy if you plumb a tee before the ball valve and then from the ball valve back to the pump intake area in the sump(watch placement for bubbles)


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[Xxero]

Melev's Reef states:

"To avoid too much flow to your tank, in case your pump is too powerful, you can put a "tee" in your return plumbing, and an elbow pointing straight back down into your sump. Then you put a ball valve on that. If the valve is wide open, the majority of your water will go straight back into your sump. The more you close the valve, the more water goes up to the tank. This is the best system, because your pump will never feel a restriction and it won't shorten the lifespan of your pump."

http://www.melevsreef.com/allmysumps.html

Example (Mag 9.5 pump):

Some pumps are designed where restriction will not affect the lifespan of the device...I do not believe the AquaMag types are one of those.

HTH. :bigeyes:

 

[Wazzel]

Melev's Reef states:

"To avoid too much flow to your tank, in case your pump is too powerful, you can put a "tee" in your return plumbing, and an elbow pointing straight back down into your sump. Then you put a ball valve on that. If the valve is wide open, the majority of your water will go straight back into your sump. The more you close the valve, the more water goes up to the tank. This is the best system, because your pump will never feel a restriction and it won't shorten the lifespan of your pump."

http://www.melevsreef.com/allmysumps.html

Example (Mag 9.5 pump):

Some pumps are designed where restriction will not affect the lifespan of the device...I do not believe the AquaMag types are one of those.

HTH. :bigeyes:

That is incorrect. All pumps can take some backpressure. Adding a valve and closing it some is no different that going higher. The pump does not know the difference between lift and a partially closed valve. If your system is set up to where you have to significantly close a valve or add a recirculation line to control the flow your pump is to big.

Also, the losses in each line will be the same. Line in parallel have equal losses.

 

[Wazzel]

Pump will last longer and use less energy if you plumb a tee before the ball valve and then from the ball valve back to the pump intake area in the sump(watch placement for bubbles)


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Nope, the Hp curves for these pumps are relatedly flat. A little throttling will make no difference in the life of the pump. You get in to problems if you throttle down past 50% and the pump is not getting significant flow through it to cool adequately.

 

[Wazzel]

I just bought a used Mag 7 (700gph) for my 40 gallon breeder tank for a return pump. When I turned it on, after a few min the water was almost to the top of my return slits and I was getting nervous. Should install a ball valve or buy a weaker pump? I understand it is hard for users on RC to judge what kind of pump people need for their different tanks but I thought I would ask for an opinion. Thanks. :uhoh3:

You need a smaller pump. A mag 7 is way more than you need.

 

[Xxero]

That is incorrect. All pumps can take some backpressure. Adding a valve and closing it some is no different that going higher. The pump does not know the difference between lift and a partially closed valve. If your system is set up to where you have to significantly close a valve or add a recirculation line to control the flow your pump is to big.

Also, the losses in each line will be the same. Line in parallel have equal losses.

What you say here makes sense to me, but so did what Melev stated.

I agree that a Mag 7 is too big for a 40b, but the " T " with a valve is an alternative solution to getting a smaller pump. I ran the 9.5 on a 40b for over a year with no issues configuring it in the same manner.

 

[Wazzel]

What you say here makes sense to me, but so did what Melev stated.

I agree that a Mag 7 is too big for a 40b, but the " T " with a valve is an alternative solution to getting a smaller pump. I ran the 9.5 on a 40b for over a year with no issues configuring it in the same manner.

Sure you can add a recirculation line to make a significantly over sized pump work, but you are wasting electricity and adding additional heat to you tank for no reason. Unless you are bypassing lots of water the recirculation line is not going to matter much.

 

[Xxero]

Good points there, as well.

 

[RWEngineer]

Pump will last longer and use less energy if you plumb a tee before the ball valve and then from the ball valve back to the pump intake area in the sump(watch placement for bubbles)


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Why will the pump use less power in this arrangement?

 

[1jwampler]

Nope, the Hp curves for these pumps are relatedly flat. A little throttling will make no difference in the life of the pump. You get in to problems if you throttle down past 50% and the pump is not getting significant flow through it to cool adequately.

Put a kill-a-watt on most any AC pump and measure unrestricted flow wattage then restrict by 50% and you will see more consumption. More consumption is more heat, which equals less life.


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[Wazzel]

Put a kill-a-watt on most any AC pump and measure unrestricted flow wattage then restrict by 50% and you will see more consumption. More consumption is more heat, which equals less life.


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If you restrict it by 50% you need a smaller pump.

 

[1jwampler]

Why will the pump use less power in this arrangement?

Simple hydraulic rule pressure is the resistance to flow. The impeller will not freewheel when under pressure, meaning it needs current(energy) to push past the resistance, like going up a hill in your car vs coasting on level ground. If you are always going up hill you use more energy to go the same distance.


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[1jwampler]

If you restrict it by 50% you need a smaller pump.

You made the argument it doesn't make a difference, now it's 50%, what about 40%, regardless of the resistance more power more heat less life.


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