I used that pump with 6 feet of head with 1" tubing. There's no way it could have done it with 1.5". Maybe with less head, but otherwise, I don't see it.
That must have originated from someone who wasn't qualified to make that statement and the technical writer didn't know the difference (typical). If you've ever seen the system work, you would wonder how some people dress themselves in the morning.
Well I needed 1 1/4" overflows because 1" would be too small at only 600gph flow through it, but you can't get 1 1/4" anything in my town, so I have 1.5" overflows lol my head is only 3 feet so i'll be getting say 750 gph with fittings.
might as well do the pump with 1.5", I already have it.
Later I can use these overflows on a bigger tank with a bigger pump.....so no sweat, some 1.5" pipes are gonna end up better lookin then HOB's I think lol
I've heard that is a common problem in the northern parts of Canada. Going bigger won't cause any problems, except for clearance issues. But you can always plan ahead for that.
Another thing im wonder is if Sluyter PVC S-40 solvent cement would be okay? all it says is for pressurised and non pressurised systems, just don't want it to killl my fish....