120rr water drop during power outages

[fishcam]

I'm doing the math to see weather my 55g with 18 in baffles will overflow if I install it under my new 120rr and the power goes out.

 

55's measure about 48x13x20, which means I have 2 inches or 624 cubic in per inch of power out water room. Multiply that by two for a total of 1248 cubic inches of power-out water overflow room. The 120rr is about double the size (48x24x24), where each vertical inch is about 1152 cubic inches of water... so my math says my 120 fish tank can drop 1.08 inch before I run outta room...

 

Therefore, the million dollar question for you guys that are already set up: How low does she go? Am I going to have to re-baffle ?!

 

thanks

 

-d

[DJBoy98]

The side of the 55g that houses the return pump doesn't have to be all the way up. You can adjust the return pump with a ball valve on the return line so that the water level is low.

 

The drainage can be controled by the level of the return pipes on the return pipes (standoffs I presume). Making it higher forces a suction break faster which will stop the drainage.

 

Just play with each time and pull the plug on the return pump and watch it settle.

Adjust accordingly.

[www.fishnreef.com]

Easy method.

Reduce the water in your sump. Switch off power. See how high the water level in the sump goes. Add the number of inches the water rises when power is off to the normal level of the sump. You have your answer.

Also, ANY algae or obstruction in the intake of the return will effectively constrict your returns leading to higher levels of water in your tank. So, when there is a power cut, that additional water also goes into your sump. Rule: Keep your returns clean.

[fishcam]

Hmm, I'll have to look when I get home. I've never had a RR before, but with my 55 that has two HOB overflows, the power goes out, air is sucked into the anti-siphon hole instantly, but water continues to drain for a bit. I'll have to see exactly how high that is though. Hopefully its a non-issue, I really don't want to re-baffle the sump.

 

thanks for the input.

[SeanCallan]

OR! To avoid power outages look into buying a UPS unit. Hook up your return pump and a heater. That should give you enough wiggle room to take action.

[lmeyer]

OR! To avoid power outages look into buying a UPS unit. Hook up your return pump and a heater. That should give you enough wiggle room to take action.

 

Good idea, but not a good answer for this purpose IMO. Yes an UPS will keep the return pump working in an outage, but for how long? What if the power outage happens while you are on vacation? The UPS will power down eventually. What if the return pump fails? I wouldn't rely on the return pump as my means of avoiding flooding. Unfortunately, I've never run a RR tank, so I can't answer the original question.

[Origami]

Therefore, the million dollar question for you guys that are already set up: How low does she go? Am I going to have to re-baffle ?!

 

How low she goes depends upon your setup. In most cases, the limit is going to be set by 1) the height of your drain or 2) the depth of your return. (2) is generally below the surface in your display, so it's the worst case. To mitigate this, we often drill a small hole that functions as a siphon break in the return, above or just below the water line, that is designed to break siphon in the event of a power outage and to limit flow back to the sump. If that break isn't there, or if it becomes clogged, you'll siphon back more water to the sump than would normally be the case. (This is a good reminder to make cleaning the hole out as a regular maintenance action.)

 

In the end, to make sure, there's nothing quite like pulling the plug on your system and seeing how things fare. Better you know now so you can take corrective action than to find out the hard way!

[SeanCallan]

Good idea, but not a good answer for this purpose IMO. Yes an UPS will keep the return pump working in an outage, but for how long? What if the power outage happens while you are on vacation? The UPS will power down eventually. What if the return pump fails? I wouldn't rely on the return pump as my means of avoiding flooding. Unfortunately, I've never run a RR tank, so I can't answer the original question.

 

I would never leave my tank unattended on vacation. Plus, use the UPS to power a device to notify you via SMS that the power is out. You call your tank sitter and ask them to go take a look.

 

Sure, it doesn't directly answer this particular question of water dropping, but it addresses plenty of other issues like the tank temp. I understand the concern for water, but a UPS would prevent the problem long enough for you or someone else to make the appropriate fix. If you limit the things on the UPS (heater + return pump) it's going to run for some time.

 

If you're not having someone come check on your tank while you're on vacation wet floors should be the least of your concerns.

[fishcam]

I would never leave my tank unattended on vacation. Plus, use the UPS to power a device to notify you via SMS that the power is out. You call your tank sitter and ask them to go take a look.

 

Sure, it doesn't directly answer this particular question of water dropping, but it addresses plenty of other issues like the tank temp. I understand the concern for water, but a UPS would prevent the problem long enough for you or someone else to make the appropriate fix. If you limit the things on the UPS (heater + return pump) it's going to run for some time.

 

If you're not having someone come check on your tank while you're on vacation wet floors should be the least of your concerns.

 

 

Well I would have thought that the height of the overflows would limit the drop, since they're the barriers between the actual drain in the tank, but with everyones comments, i'll just go take a look myself and see what it is.

 

I would suspect that a really good UPS would last about 3 mins with a pump that has reasonable turnover (~900) and 500w of heating attached to it...

[Origami]

Well I would have thought that the height of the overflows would limit the drop, since they're the barriers between the actual drain in the tank, but with everyones comments, i'll just go take a look myself and see what it is.

 

I would suspect that a really good UPS would last about 3 mins with a pump that has reasonable turnover (~900) and 500w of heating attached to it...

 

The height of the overflows are only part of it. If you're returns are submerged and are not equipped with a siphon break, they'll actually drain your tank down further through the return pump (which is off because of the power failure).

 

Do you have redundant overflows, by chance? If not, another possibility that you should consider is what happens if your single overflow fails (for example, a snail gets into the opening). In that case, the water in the cavity that's housing your return pump will be pumped dry and you have to be sure that your display can take this without overflowing. This is a greater problem in systems that use siphon overflow boxes than built-in drains, but a consideration nonetheless.

 

In the event of a power failure, besides the risk of flooding, flow and aeration seem to be the primary concerns. Heat is secondary as temperature will probably decline a bit more slowly. I don't think that I'd put a return pump or heaters on an UPS because most economical UPS units would not be able to run this additional equipment for very long.

[zygote2k]

Why not use a check valve also?

[Origami]

Why not use a check valve also?

Personally, I don't trust them in critical applications. That's a personal choice, however. Debris or deposits can interfere with their ability to close under back pressure and you're hosed.

[fishcam]

The height of the overflows are only part of it. If you're returns are submerged and are not equipped with a siphon break, they'll actually drain your tank down further through the return pump (which is off because of the power failure).

 

Do you have redundant overflows, by chance? If not, another possibility that you should consider is what happens if your single overflow fails (for example, a snail gets into the opening). In that case, the water in the cavity that's housing your return pump will be pumped dry and you have to be sure that your display can take this without overflowing. This is a greater problem in systems that use siphon overflow boxes than built-in drains, but a consideration nonetheless.

 

In the event of a power failure, besides the risk of flooding, flow and aeration seem to be the primary concerns. Heat is secondary as temperature will probably decline a bit more slowly. I don't think that I'd put a return pump or heaters on an UPS because most economical UPS units would not be able to run this additional equipment for very long.

 

No worries, my current tank has dual hob overslows, and a siphon check. I think i talked about it above... I'll be sure to include one on th 120 as well.

 

So, if there is a siphon check on the submerged returns, then the height of the overflow is the only thing that determines the amount of water overflown. I'll measure that and see if its more than an inch

Edited January 29, 2009 by fishcam

[Origami]

No worries, my current tank has dual hob overslows, and a siphon check. I think i talked about it above... I'll be sure to include one on th 120 as well.

 

So, if there is a siphon check on the submerged returns, then the height of the overflow is the only thing that determines the amount of water overflown. I'll measure that and see if its more than an inch

 

As long as the siphon break is above the overflows, that should be about right. Rather than measure, just pull the power and watch. That's the real acid test, isn't it?

[zygote2k]

Personally, I don't trust them in critical applications. That's a personal choice, however. Debris or deposits can interfere with their ability to close under back pressure and you're hosed.

I'm not saying to rely on the use of a check valve as a single measure to prevent flooding, just that you should use one in addition to whatever you decide to use. You should only use a true union check valve however as this makes cleaning them very easy.