The dangers of air pushed through a return pump

[Capslock]

Hello,

I have read that micro air bubbles is a bad thing for a reef tank; I do not fully understand why but I will take it as I go.

Anyways, I have discovered that after two days with the pump on, there was enough evaporation to cause the pump to start sucking air in.

So my first question is, how bad is this if I were at work and I came home to see air bubbles, and lots of them, being pushed into the display tank once I have fish / corals in there?

In addition to this, I only have about an inch tops between my max sump line and min line. The reason this is I found if I let the pump run and then cut off the overflow, the water will rise in the display to about 1/4" before the absolute top of the tank. This happends after the pump is finished sending nothing but water through the pipes. Once the pump starts sucking in air, there is still however a bit of water that it does suck up so I am estimating that this would account for the additional 1/4" left.

Any ideas on how to increase that min/max gap? I dont care if I top off everyday, but I would like it to have the ability to go without my intervention if I go for a vacation for a week (like in spring)

 

[metalac]

Hello,

I have read that micro air bubbles is a bad thing for a reef tank; I do not fully understand why but I will take it as I go.

Anyways, I have discovered that after two days with the pump on, there was enough evaporation to cause the pump to start sucking air in.

So my first question is, how bad is this if I were at work and I came home to see air bubbles, and lots of them, being pushed into the display tank once I have fish / corals in there?

In addition to this, I only have about an inch tops between my max sump line and min line. The reason this is I found if I let the pump run and then cut off the overflow, the water will rise in the display to about 1/4" before the absolute top of the tank. This happends after the pump is finished sending nothing but water through the pipes. Once the pump starts sucking in air, there is still however a bit of water that it does suck up so I am estimating that this would account for the additional 1/4" left.

Any ideas on how to increase that min/max gap? I dont care if I top off everyday, but I would like it to have the ability to go without my intervention if I go for a vacation for a week (like in spring)

air bubbles are NOT bad. They look ugly, that's the only reason why people don't like them. Makes your tank look dirty basically. Other than that I couldn't see any big reason why you'd want to keep the bubbles out.

As far as making the level a bit higher, try and reduce the flow of your pump. You might have a dial on the pump where you could do this, or you might use the valve on the return line, I hope you put a valve in there. By reducing the rate and which the water flows back to the tank you will increase the amount of water in the sump.

 

[Capslock]

I did not put a ball valve there, perhaps I should have. No big deal I can always install two of them at the Y split the way I set it up.


But wouldnt turning the return down effect the pumps lifespan and overall temperature of the tank?

 

[metalac]

I did not put a ball valve there, perhaps I should have. No big deal I can always install two of them at the Y split the way I set it up.


But wouldnt turning the return down effect the pumps lifespan and overall temperature of the tank?

it might, but it seems that you only need to change it a little. say go from 500gph to 450gph, so I don't think this would have a huge effect.

 

[cindre2000]

Cutting back on the outlet of the pump should not have a dramatic effect on its lifespan. However, it can help reduce the wattage used. NEVER, restrict the inlet of the pump.

 

[Anonymous]

NEVER, restrict the inlet of the pump.

yep, that causes cavitation. Destroys the pump

 

[mr_X]

do you have a hole drilled just below the water line on your return? if not, this may help with the max water line- when you shut the pump down, water is back-siphoned through the return line, as well as the overflow. this might be where you are getting the extra water from.

 

[Capslock]

The return lines do have small holes to break there siphons in the event of a pump failure, however it ends up not mattering because the overflow sucks water to the sump below the return lines anyways.

There is plenty of space in the sump if the pump ever failed, that is for sure. There just isnt that much space between where the water line is in the display and the top.

I have marked where the max should be in the event of a siphon break however if I left for 2 days this would end up going lower than the pumps inlet so air starts getting pushed through. I am trying to find a way to increase this gap so its no problem if I go away for a week.

The prior owner had a max fill line on the sump thats about 3 inches higher than mine. I am wondering if this was just him taking a chance.

 

[Capslock]

Also,

Doing the math, I am losing about 1/4 of a gallon per a 12 hour period, so of course 1/2 gallon every day.

Does this sound normal to you?

 

[metalac]

Also,

Doing the math, I am losing about 1/4 of a gallon per a 12 hour period, so of course 1/2 gallon every day.

Does this sound normal to you?

I loose about that much on my 55.

Also try shortening the return pipe, so it's only about an inch below the surface. I ended up doing that just in case the little hole I drilled below the water line gets stuffed with algae or something and doesn't work.

 

[Slayer]

Can't you just add more water to the system. Fill your sump up? What are you using for a sump? I have one of those blue plastic totes from Wal-Mart.
And it over 1/2 full. Also, is you your overflow not working correctly? It shouldn't ever brake siphon.
And on another note, I don't know if I would go away for a week if I didn't have someone check on my tank every couple days.

 

[mr_X]

i would not let your return pump suck any air. it will most likely drastically shorten it's life. i would also consider an auto top-off device, with the situation you described.

 

[Anonymous]

You can also put plumbing on the intake of your pump which starts with an elbow turned down towards the bottom of the sump. This will allow for more time before the pump starts cavitating. Try not to put the elbow right at the intake if you can help it. But, if you have to, try sizing up the plumbing size with an adapter and then place the elbow.

Good luck.

 

[Entacmaea]

Trying to understand the problem here, and a couple fundamentals seem to be missing- the water level in your display tank is controlled by the level of the overflow (if using a surface skimmer design), and the rate at which water is leaving/entering the display tank. So, if you have added less water in the sump as a hedge against your pump not overflowing your display tank, it seems that your weak point is your overflow- it should be fool proof- in other words, it should never fail, so your tank never overflows. There are several fool-proof designs out there. When your return pump turns off, water will drain into your sump raising its level, and that should stop when either your siphon breaks, or the disply tank water level drops below your surface skimmer "box". Either way, your sump needs to have enough "room" in it for this "back siphon" in the event of a pump failure.

You can always just add water to your sump, as suggested, to raise its level and prevent evaporation from letting your pump run dry. With a fool-proof overflow, you then don't have to worry about the pump ever pumping too much water into the display. This is, of course, assuming that your overflow rate is higher than your return pump, which should always be the case (helps in case something obstructs your overflow- like a snail).

Make a fool proof overflow, and problem solved!

Thanks, Peter

 

[Anonymous]

Trying to understand the problem here, and a couple fundamentals seem to be missing- the water level in your display tank is controlled by the level of the overflow (if using a surface skimmer design), and the rate at which water is leaving/entering the display tank. So, if you have added less water in the sump as a hedge against your pump not overflowing your display tank, it seems that your weak point is your overflow- it should be fool proof- in other words, it should never fail, so your tank never overflows. There are several fool-proof designs out there. When your return pump turns off, water will drain into your sump raising its level, and that should stop when either your siphon breaks, or the disply tank water level drops below your surface skimmer "box". Either way, your sump needs to have enough "room" in it for this "back siphon" in the event of a pump failure.

The return plumbing for the water going to the tank from the sump also becomes a siphon once the power is cut. This is the problem, not the overflow box. The sump is filling until the siphon is breaking in the return line.

 

[Entacmaea]

That is going to happen anyway- because your return outlet is submerged, right? If it is submerged just 1/2 inch below the water, your sump should be sized to handle that much back-siphon. (I usually don't drill the siphon break hole, because it increases noise, saltspray, etc. and if that hole gets clogged.. its just another failure point) Then when the power comes on again, the water gets pumped back up and your overflow reactivates (right?), starting the loop again automatically. Using a surface skimming box, for instance, means that your display will never overflow- which is nice peace of mind, trust me!

Here is a link to an auto-top off system, which is easy to make (and costs about $10 bucks), has no moving parts, and is, yes, fool-proof! (See my theme!) Ironically, it uses- a siphon... lol. Based on your evaporation, a 5-gallon jug could give you about 10 days top-off...

http://www.cs.cmu.edu/~cap/raid/topoff/ ... index.html

Hope this helps. You can fiddle with the return pump rate, adding valves, etc. as advised, but having an over-sized, fool proof overflow is the easiest and safest solution...

Best, Peter