Ball valve on overflow side?

[AZDesertRat]

You will not have any problem with it losing siphon if its a U tube style overflow box and not grossly oversized which yours is not. The eshopps overflows are very reliable.

 

[Dtech07]

Thanks for confirming my thoughts AZDesertRat i had a similar Q&A but you covered it nicely.

 

[totion]

Thank you all for the help

 

[jm23]

I put a valve on every outlet and inlet to my tanks. You never know when you need to do maintenance and have to shut them off. Otherwise they are wide open as has been said numerous times above.