pump noise

D&KSac

D&KSac

Premium Member
I have a mag 7 return pump on my tank and had to replumb it exturnal because it was raising my temp in my tank an average of 2-3 degrees. Since doing that i have noticed that it is starting to get really loud. Are these pumps not made to be exturnal? Is there a way of plumbing to lower the stress of the pump so it doesnt have to work as hard to pump the water? Or are these just loud outside the water? I dont want to burn up my pump if these arent designed to be exturnal and may just have to deal with the temp.
 
I ran my mag7 externaly because of the same reason. I dont know why yours is louder when you have it external, mine alwase ran quieter. I just set it on a rag or small towel to muffle the vibrations. I would still run it external but i have cracked a few of the outlet houseing and cant do it anymore :D. Do you have a ball valve on the outlet side of the pump? If so, this could/will overstress the pump. They are just loud pumps overall, im planning on an upgrade soon.
 
IME with various Mag pumps I don't think they're at their best when run external, and the only one I've ever had that failed was being run external on a pond. The plastic was distorted, which indicated overheating.

I posted suggestions about reducing noise from mag pumps in the thread about Harmonics

For a long time I was running a mag pump semi-submersed. It was on an acrylic shelf in the sump and it got wet occasionally, and was always submerged during the months when there was no danger of overheating the water (house was cooler).

Also, the amount of problem from overheating will be due to how large the pump is relative to the volume of water in your entire system. I expect you'd have problems (during the warmer months) running a closed loop system with a submerged pump large enough to do that. My pumps are only large enough to take care of the skimmer that is in the sump. I don't know why you'd want more flow through the sump than that.

I run my reef at 80 degrees (the best reefs I've been on underwater were all at an annual average of 78-82 degrees) and because my house is rarely above 80 degrees, the two submerged pumps I have are unlikely to raise the water temperature above that. A good fan on the lights is far more important.
 
They are designed to be cooled this way. The heat generated is a function of the mechanical efficiecy of the design, that when selecting this pump must be weighed against the reliability of it. Which is why they are "good" pumps to buy.

If this is on your 37g, a mag 7 is probably to big for the system and because it doesn't have enough water volume to asborb the heat. The is the reason you are seeing a one to two degree rise while using it. I use a Mag 7 for the return on my 75g with a total water volume of 90g or so.

Shoot for a lower flow rate through your sump, 10X or so. People get hung up on super high flow rates through the sump when they are not needed. In fact, you want the water to slow down a bit there and allow the stuff to fall out of solution and be collected by the filter sock and/or skimmer and not hang out in the display.

Buy a smaller pump to replace the one you just burned up or drasticly cut the reliablity and service life of.
 
Last edited:
WarrenG,

Sounds like you got lucky or just had to buy a new pump twice as fast.

Water and air do not disapate heat at the same rates. 80 degree water and 80 degree air are like apples and oranges in terms of heat capacity and transfer.

One example of this:

The Conductivity in terms of Heat Transfer of water, not saltwater, at 300 K, and 100 kPa is .60 k (W/m K) and Air is .026 k (W/m K).

This property shows water to conduct heat 23 times more than air.
 
Last edited:
I know that air doesn't transfer heat as well as water, but the manufacturer claims (probably erroneously) that the pumps can be run non-submerged.

As far as keeping the tank warmer and that impacting the effect of the heat transferred from the pump, it takes much more energy to raise the tank's temperature 10 degrees above the ambient room temperature than it does to raise it one or two degrees above ambient room temperature.

If the room is at 78 a proper-sized pump probably won't put the water over 80, but if the room is 75 the pump definitely won't put the water over 80. If you aim at 78 for the tank you're more likely to swing above that target due to the heat from the pump and the lights.
 
I think im just going to replumb it back into the sump and maybe get another fan to help dispurse the heat when the halide is on. I really dont want to burn up the pump and it just doesn't seem to be opperating as well as it did when it was submerged. Thanks for the imput guys.
 
I agree with everyone else, and you. Mag pumps may claim to be external/internal pumps, but the truth of the matter is that they suck when they are external. They crack easily on the return side, and once they heat up they lose gph.

Put it back in the sump and add an extra fan.
 
Yeah thats what im gonna do, putting it back into the sump seems like what i need to do. Im starting the build and gathering of parts and pieces for my 120 gal. Accually spent the last 2 hours on Marine Depots website buiding a wishlist and watching my cart $$ amount go up and up and up. lol But this is sure gonna be fun to do it right.
 
The fan for the lights... in the summer time I have the fan pointed between the water and the lights for maximum cooling (including evaporative) when the house is warmer. As the house gets cooler (the lights are less likely to overheat the tank) I point the fan above the lights. And from now until the spring I leave the fan off and let the lights heat the water during the day so the heater doesn't have to be on as much.
 
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