Plenty Of Problems

[DevUK]

I'm starting to use 2 DIY soda bottles. You need a "T" connector and some CO2 tubing (like air line, but CO2 resistant), also a non-return/check valve would be good.

Join the 2 DIY bottles togther with the T piece and then connect to your bubble counter/diffuser. Check valve should be inbetween your bubble counter and your diffuser.

 

[BHornsey]

Hi,
I think you're in the States, so Rex Grigg is the place to go for CO2 equipment or Greg Watson.
Valves are not hardware store stuff.
In the UK, Aqua Essentials are good.
Rex Grigg's parts
Aqua Essentials