Does a return pump warm the water?

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Peixe

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Apr 19, 2012
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Hi guys,

I have a 75g sw tank, with a couple of corals and a few fish. Everything runs fine, numbers are good except for temperature. It is always high (+-84F) lately and I never had that experience before, since house temp is normally 70 or so, Seattle... I run a Mag Drive 9 or 9.5 I think and I noticed that if i turn it off the temp goes down. Is it because of less flow or may it be the pump itself? Help please
 
I notice with a big pump i have to mix salt water it warms the water a little!!
As long as your temperature is stable it should be ok!!


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84 is a bit high. I would want it 80 or below if possible. Yes, any pump you add to the tank will warm the water, though I haven't experienced that kind of heat from a mag 9.5. Are you sure it's not coming from something else? What lights are you running? Though if you are turning it off and seeing the temp fall, the heat is coming at least partly from the pump.
 
Here's a 3 min video from BRS discussing some differences between external, internal, and dual purpose pumps in terms of ease of installation, application, construction materials, and heat transfer.
In a test conducted in 5 gallons of 79 degree F water over 3 hours, the external pump raised the temp 7 degrees while the internal raised the temp 16 degrees. Not saying that the internal pumps are bad, they just need to be factored into your heat management plans.


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The above link does not seem to work with mobile devices :( Maybe it's just me. Let me try it again:
watch



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Submerged pumps add significantly more heat than external ones do, like twice as much for the same flow. Easy to see why as the motors water cool unlike external pumps that air cool.

Pumps add heat.
Lights can add a lot of heat.
Even biological process's add a bit of heat.

I agree, 84f is too high IMO.


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Not for nothing, I recently ran into the same problem and found out that my heater wouldn't turn off. Even if I turned the knob way down.

In my 90 gal I have a Mag 12, Koralia 1450, and run a Tek T5 4-bulb and that seems to add about 3 degrees.


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Save up, get a JBJ chiller. Probably run you 350 for your size. I tried maintaining temp with fans and ice until I lost coral. I bit the bullet and got a chiller. No problems no mo.

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Hi guys,

I have a 75g sw tank, with a couple of corals and a few fish. Everything runs fine, numbers are good except for temperature. It is always high (+-84F) lately and I never had that experience before, since house temp is normally 70 or so, Seattle... I run a Mag Drive 9 or 9.5 I think and I noticed that if i turn it off the temp goes down. Is it because of less flow or may it be the pump itself? Help please

If your Mag 9.5 is used submerged it will heat the water. Nice things about Mag pumps is they can be used external too, reducing the chance of heating the water.

Dick
 
I would do some research re using mags externally. I've been told by several hobbyists that they don't work as efficiently out of water and that's not the ideal application.

However, I have my return external and I still had heat issues.

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I’ve used various sized Mag pumps both externally and submerged for many years without noticing any drop in efficiency. My only complaint with Mags is the energy they consume.
 
I'm not saying it can't be used that way, but you proved the point made about efficiency - energy consumption. Since they aren't really built for that, they work harder.

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Not true! They are energy burners in any application and they are built for that. That being internal or external applications.

Dick
 
I will definitely have to run a chiller. I will do some research anyway. Tonight I am not running the skimmer and the 2 heaters are unhooked from power outlet. Will see how it looks (temp) in the morning.
Then if there is no changes, I will stop the return pump for a few hours and keep track of temp... I really wanna know why this is happening since the tank is almost 2 years old and I never had this issue b4. Also temp is not that hogh in Seattle's fall...! Will keep you guys updated.

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after much research I settled on the Sicce Silent line of pumps.
They are specifically designed for either application and thus far I have 0 complaints or issues.

Having considered the heat issue and after struggling with high temps this summer, I decided that when I revamp/upgrade my saltwater, I'm going to configure the sump for both an external and submerged return pump. That way when the ambient temps start to climb I can use the pump externally and save a few degrees of heat.
The reverse is true for winter, and I will benefit from the heat generated by using it submerged.
all it will require is a bulkhead fitting and valve on the sump. (y)
 
If there is a restriction or too much back pressure, even magnetic drive pumps will consume more power and as a result create more waste heat.


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IME pump will heat up more when subjected to higher than its capacity. Meaning more flow requires more power thus radiates more heat. Restricting the flow does not necessarily mean that the pump consumes more power instead it is the opposite. A larger size of pipe in its inlet/outlet and with less head height will have easy flow but you will get more heat. Try installing a gate valve and reduce flow. If it does not reduce heat then there is something wrong with your pump.
 
Does a return pump warms the water?

I don't agree. The more energy used to lift or push the water the more waste heat the pump will produce. I think if you put a amp meter on your pump and restrict the flow you'll see it using more power. Placing a load on any motor causes it to draw more current and as a side effect, create more heat. But that's just my opinion.

How does a pump exceed its designed flow rate? If anything they struggle to do as advertised, not run away RPM's. Maybe I misunderstood your post.


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I think if you put a amp meter on your pump and restrict the flow you'll see it using more power.


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That's exactly what I am about to suggest. I am 100% sure you will get the result as I have mentioned because I have done this before. When you restrict the flow there is less water being pushed up therefore you use less power not more. Similar to electricity, high resistance less current so you consume less power.

.
 
it really depends on whether you pushing or pulling the water.
If you are pulling the water with the pump and the INTAKE is restricted, the pump will not necessarily be working harder as it can only work with the flow of water it is being delivered.
If the pump is pushing the water and the output is restricted, then it will be working harder because a greater volume of water is being presented to the pump than it can push through the restriction.
Same principle as dealing with head height.

but the above conditions would be more likely encountered in a closed-loop system and not so much a sump as you can not "force" water into the pump in a sump.

pulling water always requires less work.
 
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