Will this return plumbing cause problems during loss of power?

[Bacchus]

I recently purchased a pre-plumbed 90 gallon acrylic tank (with sump/stand) from someone. I noticed that the return line went up through the bottom, back (in the back plumbing housing area). The return pipe goes up near the graded overflow, does a 180 degree turn, goes back down, then goes out of the housing about 2" from the bottom where it is split. Each split runs along the back and has holes pointed forward and up. I have never seen this setup before and asked if it would flood if loss of power, to which he replied no. I am still apprehensive about this claim and am considering a modification to place the split near the surface, similar to others I've seen, enabling air to get inside the plumbing, breaking the vacuum during an outage. Am I wrong about my apprehension?

 

[Peppie]

There needs to be a siphon break near the top of the return line.
Check to see if there is a hole drilled on the underside of the return line at its highest point in the overflow box.
IMO it is a flood waiting to happen. If any thing covers the siphon break hole you tank will drain the tank to the height of the return nozzles.

 

[user 26995]

I agree. even if there is a hole drilled in the top of the return line, I wouldnt trust it. is there a check valve on the return line?

 

[Bacchus]

I noticed two adjacently drilled holes (circumference of my cell phone charger cord) just below the first 90 degree top elbow. No check valves. I guess even if this did prevent a reverse suction into my sump, it ineffectively sends some of the return flow (out of those two holes) directly down the drain vice into the display tank during normal operation. This coupled with the added plumbing length and multiple 90 degree elbows currently required to reach the top then bottom of the tank, seem like an unnecessary attenuation of the return flow. I think I will just modify the return plumbing to have it exit near the water surface. Maybe for curiousity fulfillment, I'll measure the flow rate with this current set up (I have to clean the tank anyway) and compare it to the rate after the modification.

 

[user 26995]

Yeah, those holes would pull enough air to stop a reverse siphon. I can kinda see the reason for doing it the way they did. But I like having my return set right on the surface for added surface agitation. I personally would replace it too.