Bob,

ok...now I'm learning something. I always thought that 'schedule' referred to a combination of O.D. and I.D. but apparently, after a little research, that's not right (1.5" schedule 40 and schedule 80 pipe are both the same O.D., but different I.D.). As you point out, schedule is simply a wall thickness that affords a particular pressure rating -which I don't need.

The issue I have is that right now, I have the pipe and all the fittings (except the Tee) in white and all schedule 40. I'd be happy enough to switch all that to a grey PVC of whatever schedule (or none) as long as I can get all the bits for that to match up (and fit). I have no idea where to get the other pieces in grey !

I wasn't going to glue any of this in case I ever need to take it apart (and since there's no pressure to speak of, I didn't see a need).

If you have a chance to look and see if you have the white pieces, I think that would be my simplest solution. Otherwise, I'm open to suggestions.

Thanks for the help.

I will have a look. if I cannot find any white, send me a pm of what you need. You will just have to pick it up in south cowtown on the weekend, have to stay here this weekend, have a tank to build.
Do yourself a favour and glue everything up, I know that there is only head pressure on the system, but...... Murphy has a way of showing up at the most inconvenient time.
I get the feeling that the piping will be exposed?? Hence the need to keep everything the same colour?
Also schedule number is an indication of pressure rating, it is directly related to the wall thickness. So what you have so far is all pressure rated fittings.