<a href=showthread.php?s=&postid=14916342#post14916342 target=_blank>Originally posted</a> by drummereef
Thanks Marc. Well dangit, I figured there would be some leakage but now I know for sure. 
Back to the drawing board... I remember reading about the pvc gluing surface area. If I remember correctly it's the DWV (drain/waste/vent) stuff that is not pressure rated and has a shallow socket. Savco will definitely be getting sick of me over the next few weeks. 
I'll hit Pete up as well. He's well versed in manifolds from what I understand.
the design looks good, some comments
With a good pump that delivers a good flow at a decent pressure, the sweeps don't gain a whole lot. Sweeps on drain lines are a huge benefit as you only have gravity moving the water and you need to allow for air to escape.
when a system shuts down (eg feeding mode) it's inevitable you will get air in the pipe all the way down to the sump level (both drains and returns) your design blows most of the air to the returns but you will get some on you reactors. The only way to prevent an elevated (higher then sump level) section of pipe not to drain is to have both ends below the pump off sump level.
So, the only for sure way to prevent air burps in reactors is to have the supply tee from the pump located below the sump level and to have the reactor outlet lines empty into the sump below the sump water level. This approach provides a liquid seal.
a way to help minimize reactor burp would be to put a recirc line at the end of the header run. Most of the air will try to run to the last and highest exit point. If you go this route you want the reactors to create liquid pockets that don't syphon. The return lines should return to a point higher then the reactors and be open to the air. This can be done by hanging the reactors on the outside of the sump, or place them in the sump, or if elevated above the sump use a stand pipe for the return lines that is open on top.
other common suggestions I make:
design your drain lines first, minimize all turns, use hard pipe for horizontal runs and install with a slope of 1/8 to 1/4 " per foot. Use drain fittings (sweeps). Spa flex sags on horizontal runs and creates dips and high points that create air pockets and will slow the flow and may gurgle. Think of your drain like a water slide.
keep your pump suction as short and straight as possible
no check valves, they are a failure point, design the system to completely drain to the sump level
make sure you can drain your display (or elevated refugium) as fast as you fill it
union ball valves are more expensive then they are worth (IMO)
design all piping to be removable with unions or threaded where unions don't work
I'm probably forgetting some things.
Love the design :thumbsup:
