3 liter bottles?
 

hello ron, I really enjoy this site! was wondering what modifications would need to be made to your 11 plant system if one wished to have 9-11 plants in 3 LITER BOTTLES? what pvc pipe size would you recommend, would a larger overflow valve or anything else be necessary? thanks again

You will have to take a bottle cap with you to the plumbing store and check the sizes until you find one that fits without to much modification. You can use two overflow pipes if one isn't enough or use a flow control valve to slow the flow if you pump is to big for your system.