Need answer on one way check valve

I just helped my neighbor convert her 46g bow from fresh to salt using a hang on back overflow box--All is running great and plenty of flow. The problem is when I pulled the plug to simulate a power outage, the hang over the back nozzle from the return pump starts siphoning backwards through the pump into the sump. It would be ok but it drops the tank almost 2-3 inches until the water goes under the nozzle. Is there a in line one way check valve available?? I searched and keep coming up with air check valves--My overflows have a hole drilled on the under side of the 90 degree elbow. Drilling a hole in this is not an option--too close to the rim. Suggetions please!!!!

 

I'm not sure I understand completely why drilling a siphon-break hole just under the water surface on the return plumbing isn't an option. Can't you disassemble the return plumbing? That seems to be the defacto way of handling this problem in my experience.
If you can't disassemble the plumbing for cleaning you might want to reconsider that first because that might be a bigger issue, I think plumbing generally needs to be maintained periodically to make sure it's running optimally and isn't a flood/failure risk.

From what I've read check valves in marine aquariums tend to get clogged up with calcium/carbonate precipitates/algae etc and eventually may fail unless you religiously clean/test them.

 

As screwtape said, you can drill a siphon break.
Also, here are your check valves:

Plumbing Parts > Saltwater Aquarium Supplies

Check Valves

 

You can get a check valve, but they do not work reliably in a saltwater environment. Doing the siphon break hole is a much much better idea.

Kim

 

I put a check valve on my friends tank along with the small holes in the Loc-lines just to be safe about a year ago. He has had two power outages and he said it saved his floors and fish.

 

Well I thank you all for your great advice and went with drilling a hole--The thing is that the pipe down to the nozzle is only about 2 inches--I drilled the hole just under the water surface and when we fired up the pump it was spraying just under the rim. I slid a piece of 3/4 pvc about an inch long to cover the ho;e but still lets air in. WORKED PERFECTLY!!!!! The siphon breaks instantly as soon as the power is off with almost no water loss!! Thanks again.

 

Just wondering if anyone uses check valves in their supply from sump/fuge?

 

As KGross said above, they don't work so well in a salt water environment. They may work at first, but as calcium and other materials build up on them over the years, they can easily become stuck open and not work correctly. They might have to cleaned in vinegar every year or so along with your annual pump cleaning to remove deposits. It just may be more trouble than it's worth, but you do what you want.
I'd always prefer an internal overflow setup over a siphon system to be safer.

 

Not to mention they reduce water flow.