Plumbing Question

[Dakafall]

I just finished my DIY stand for my 5.5g, and it's donna have a 2.5g sump, since i'm really tight for space in the stand, i was wondering if it'd be possible to drill the bottom of the 5.5g and run my return through that, the pump i'm gonna use is some sort of mag-drive, i was wondering if I would end up with my tank drained onto the floor if the power died

I've got pics if anyone doesn't understand what i'm talkin' about

[BrokeColoReefer]

Well, without a check valve your tank will drain into the sump, unless you buy a threaded bulkhead and return the water at the top. You can use a check valve but its never a good idea to realy on mechanical means of stoping siphon.

[Dakafall]

do they make check valves for 1/2" PVC? if so where could i find one?