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View Full Version : Back flow w/ a power loss?


Dollarbill
04/19/2006, 08:09 AM
I noticed when I shut the power off my sump started filling. It was a back flow coming in from my tank down to my Pump and back into the sump. Is there a quick fix for this? Maybe a 1 way valve or something? Thanks for your help. db

Johnic
04/19/2006, 08:51 AM
Check a check valve..marine depot sells it..buy the true union version

smleee
04/19/2006, 09:08 AM
Check valves can and will fail, it's just a matter of when. Drill anti-siphon holes in your return lines (if you don't have bulkheads), or if you do have bulkheads always leave enough room in the sump to compensate for the backflow.

eee

Dollarbill
04/19/2006, 09:21 AM
Where do i drill them? My return water connects through my overflow to 2 lines that I can direct in almost any direction. Thank you. db

E-A-G-L-E-S
04/19/2006, 09:23 AM
spring-loaded check valves will fail but not the kind with the rubber flapper-IMO

ricks
04/19/2006, 09:54 AM
No check valve is safe... Always make sure your sump can handle, your backflow. It's easy to check, just turn off your pumps.. Drill a siphon break or add a piece of pvc to your overflow bulkhead...

Dollarbill
04/19/2006, 09:55 AM
where do i drill the siphon break? db

jgoodrich71
04/19/2006, 09:55 AM
Anything mechanical can fail. Drill a small hole in the PVC inside of your overflow box at the top. Usually there is a T or an elbow that the modular tubing connects to. Just drill a small hole there. The idea is to break the siphon by allowing air to enter the return line. Otherwise, it will siphon until air can be drawn into the return. It's also not a bad idea to make sure your sump can handle whatever volume of water will backsiphon from the tank, just in case this fails also.

So, if you want to be extra safe, make sure you have a large enough sump, put a swing check valve inline, and drill a siphon break in the returrn.

mayor10
04/19/2006, 11:49 AM
How big does the siphon-break hole need to be?

smleee
04/19/2006, 12:20 PM
<a href=showthread.php?s=&postid=7206148#post7206148 target=_blank>Originally posted</a> by Dollarbill
where do i drill the siphon break? db

You want to drill it a hair below the water surface on your return tubing in the tank. Try to drill it so that it will point downward and not spray water upwards above the water line. When the pump turns off, the water will drain to this level and the air will break the siphon. You may still have more water going into the sump because the height of water in the display tank may still be above the overflow teeth, so it will drain until no more water will go into the overflow.

1/8" usually does the trick.

eee

artis
04/19/2006, 12:44 PM
Just wanted to second those posts on the need for a small hole for a siphon break. You'll want one on the return particularly, because the overflow will stop as soon as the water level drops below the "teeth".

One particularly important maintenance issue relates to keeping the hold clean. You'll want to check him every few weeks. Snails, slime, coraline, etc will plug that hole up. If that happens your siphone break will no longer function.

Recife
04/19/2006, 01:55 PM
Dollarbill, the syphon just happens because there's no air in the tubing. Once air gets in you will break the syphon.
An alternative to avoid drilling the return pipe is to have it placed close enought o the surface so that when the water starts to go down it will expose the pipe opening and it will stop the syphon.
I have two return pipes coming from the same pipe as in a Y connection. I placed one of the returns high up and one further down. It works perfectly for me and it's flawless.

If you prefer to drill, any hole size big enough for air to come in will be sufficient.

spidey69
04/19/2006, 02:07 PM
I had the same problem. I drilled my hole just beneath the water line on my PVC return. It's not a large hole just enough for air to get in. I think if you drill it to big the water will return through that hole (and you'll have it spraying across the top of your water) and not your main one.

rustybucket145
04/19/2006, 03:13 PM
Not a real solution, but I installed a T valve on my return. I can shut it off during maintenance. I know if the power goes off I'm up the creek. But for maintance it works great.

Dollarbill
04/19/2006, 06:36 PM
Maybe you could leave it cracked open a bit, and if you do lose power your line will fill with air instead of continous water?

E-A-G-L-E-S
04/20/2006, 09:40 AM
<a href=showthread.php?s=&postid=7206149#post7206149 target=_blank>Originally posted</a> by jgoodrich71
Anything mechanical can fail.

...there's nothing mechanical to the rubber flapper?

AZDesertRat
04/20/2006, 11:12 AM
Its still a moving part that can and will get coated with slime and fail unfortunately.
One key thing that has not been mentioned is ALWAYS leave enough freeboard in your sump to contain any backflow water from the tank in a worst case scenario. Paint a mark on the sump and never ever fill it above that point. Check valves fail, siphon break holes get plugged with algae or even a snail can cover the hole and you have no protection. Recife's suggestion to keep the returns up high so they break the surface about the same time the overflow fingers dry up is good advice.

smleee
04/20/2006, 11:40 AM
<a href=showthread.php?s=&postid=7213737#post7213737 target=_blank>Originally posted</a> by AZDesertRat
One key thing that has not been mentioned is ALWAYS leave enough freeboard in your sump to contain any backflow water from the tank in a worst case scenario.

Hey! I thought I did! :) Or is "freeboard" something different?

<a href=showthread.php?s=&postid=7205829#post7205829 target=_blank>Originally posted</a> by smleee
always leave enough room in the sump to compensate for the backflow.

eee

jgoodrich71
04/20/2006, 11:53 AM
<a href=showthread.php?s=&postid=7213951#post7213951 target=_blank>Originally posted</a> by smleee
Hey! I thought I did! :) Or is "freeboard" something different?

No that's the same thing that you, I, and ricks said. He just wanted to use freeboard to sound like he knows what he's talking about.:lol:

Freeboard is usually used for boats: the side of the hull above the waterline.

And EAGLES, if something has a moving part, it is mechanical. If you believe that it will never fail, you are mistaken.

Amphiprion
04/20/2006, 11:57 AM
<a href=showthread.php?s=&postid=7213150#post7213150 target=_blank>Originally posted</a> by E-A-G-L-E-S
...there's nothing mechanical to the rubber flapper?

Sure there is. Anything that moves in some fashion or another in response to something is technically mechanical. Any kind of flapper is a mechanism.

Dollarbill
04/20/2006, 12:28 PM
Going to put a ball vavle on it today at lunch time between the pump and the tank on the return to help slow it down. Also going to add a double drain tube. Thanks for all of the help. db

Dollarbill
04/20/2006, 03:15 PM
Got it!

E-A-G-L-E-S
04/20/2006, 09:04 PM
my buddy's 180g has a check on his return that hasn't failed once in over 4 years. i was just trying to say they are much more reliable than spring loaded ones.
and since the average time people put in this hobby(around 1 year) it shouldn't fail in that short time frame.

Of course having room to spare figured out when building sump is mandatory ;)

Dollarbill
04/21/2006, 07:27 AM
Ya, i think im going to put on a check valve just for good measure.
It wont overflow now (the tank) and i put a ball valve on the return side of the pump to slow the damn pump from running the sump dry. The outlets are close to the top and i've checked it several times now to suck air in immediatly after a power loss. (we just got new carpet... i had to). Well its cycling now and probly buy lfs water next week. Tanks to all for all of your help! db