3/4 pipe instead of 1 inch
 

Hi Ron, I have started to build your 11 plant 2-liter system but had problems finding 1 inch piping instead I found everything in 3/4 inch will the 2-liter cap fit this and if so will it leak
Thanks
Pingman

You can use 3/4 inch if you don't use the bottle caps and heat up the tee to make it pliable and cram the bottle into it.
Or grind a little off the threads and then glue them in.