Like I said I learned allot about why commercial canisters are made the way they are most especially the lid O-ring that seals on the side instead of the top or bottom of most commercial canisters.
If an O-ring only seals from the bottom of the lid like my DIY it can take allot of negative pressure (powerful pump) but it cannot take more then about 7 PSI positive pressure (siphon tank pressure) and why my canister is siting on a stool 1/2 the depth of the aquarium only. Any lower then the bottom of the aquarium and the positive pressure at 10 PSI will start to push up on the bottom of the O-ring If the power is shut off (power outage) and leak past. This is why most canister filters don't place there O-rings on the top or bottom but on the inside or outside edge between the lid lip and canister rim. This way water pressure cannot act on the O-ring, the clamps are simply there to hold the lid in position mostly.
This is why you hear stories about people who's canister filter started leaking all over the floor during a power outage. The O-ring was not seated properly, moved off its side position on the canister, or needed replacing. As long as the pump was running negative pressure kept the water inside even though the O-ring was compromised, but once the power was lost positive pressure built up to 12+ PSI and because the O-ring was not in place or pinched water pushes its way past the lid crack all over the floor until the aquarium is almost empty.
So always test your canister filter after cleaning by running it for a few minutes then turning it off for a minute and giving it a shake and check for leaks from an out of position O-ring, cracked O-ring, pinched O-ring, shrunken O-ring, and last but not least a dried out hard O-ring.
