Nice Cheap DIY Overflow

The inside pipe and the outside pipes don't actually need to be the same length. As long as the outside is longer and the "T" that breaks the siphon and allows the water to enter the discharge hose is even or higher than the bottom of the inside "U".
The thing seems to work best if it is about half the depth of the tank. If it is too short the siphon seems to be weak, like when you are siphoning the last bit of water out of a bucket.
It seems to be best to make these with 1" or 1 1/4" PVC. If you go larger the velocity of the water passing through the "Siphon Bridge" seems too slow to pull out trapped bubbles. I made one once from 1 1/2" pvc with a slow overturn of only about 80 gallons per hour. I had to draw out air bubbles daily.
I also made one using 1/2" CPVC it would get "vapor lock" from bubbles in the tubes. They were just too small.

Aquayne
Wayne Johnson
Logan,WV USA

 

Welcome to 3reef Wayne! ​

And thanks!

Mike

 

Covey, here is a picture of my overflow. For mine, I straightened the inner tubes to lie flat against the end of my tank. Also for the 'U' turns, I used a regular elbow and a street L that narrowed the width so it really hugs the tank as it goes over.




Mike

 

That is a good idea but i just twist the unit so that the 3 "U"s look like a "Z" when viewed from directly above ".

Aquayne
Wayne Johnson
Logan,WV

 

OK, I'm gonna poke my head up to be shot at here, but I'll ask the question. If the power fails and your pump stops, how does the siphon restart? Is there some sort of self priming or doesn't it lose the siphon in the event of a power failure?

 

;D (Well, you didk ask!)

If the power fails, the level ine tank falls until the siphon is broken by air entering the drain. The 'T' on the outside, combined with the vent stack stops the siphon break before the air can break under the bottom 'U' in the tank. This leaves the over the tank 'U' filled. When the power starts back up and the water enters the top drain again, there is enough suction to clear the air in the drain tube.

Mike

 

Very clever, and a nice use of smileys aswell.:clapping:

 

There must be water in BOTH "u"s. If not air can get into the Top bridge over the side of the tank. This is exactly how the big acrylic units work, just more complicated to make.

You can remove the inside "U" and riser intake tube. The water will just fall to the level of the outside "siphon break T". The down tube must be long enough so that it never takes in air. This can be used for Fry tanks or other tanks where the level is lower. A turtle tank comes to mind or a Betta breeder tank.

 

How do I post pictures?