Builder says originally how there are no 90 deg in his pool. Then when plumbed I brought some in the steel to his attention and he said oh no the returns can have 90's just not feeds. He said to prevent a 90 he uses a swoop 45. Ok I buy that but today after a lot of plumbing is put in I went out and find several feed lines with 90's. Of course they had buried the joints but i uncovered them when I got curious. So when is it ok to use 90's?

It is ok to use 90s wherever you need them and it really doesn't matter where you put them, they will have the same effect no matter where you put them. They have about twice the head loss as a 45 or swept 90 but even so, it is usually not worth the effort or cost to use them instead of a 90 unless you have a ton of them.

My understanding is that it's an optimization problem -- first get large enough pipes, then put in the easy turns, if you have to put 90's in a few places...probably OK, they will hurt most only at high speeds (e.g. solar) when small changes in head loss require increases in pump power. The contract with my builder required lazy turns wherever possible, but we still ended up having to put in a several 90's at the equipment pad just to keep the piping from getting unmanageable with all the various connections.

Increasing pipe size will gain you more in efficiency than changing from 90s to swept 90s. For example, replacing 10 90s with swept 90s might gain you 1% in efficiency but upsizing the pipe from 2" to 2.5" while still using 90s would gain you about 3%. Of course doing both you gain you about 4%. Either way it isn't a lot of savings. The pump size/speed has a much bigger impact.

this thread reminded me of these pics

That's what I call over optimizing! But hey if you're going to go big you may as well go BIG!

I'm glad we used 90's, that looks really messy.

Yeah I think using the sweeps instead of 90s is a bit of gilding the lilly. Just use a smart layout and I dont think you are going to be unhappy with using 90s instead of sweeps. It would be a loooooooong long time before the difference in efficiency would pay for the difference. And if you just have money to burn, there are better places to optimize the efficiency.

Just my 2 cents.

OK thanks I feel better- I just wish they would not make a big deal out of how they use 45's then use 90's when it make little difference- The discrepancy just makes me question them on little things. I guess I need to just sit back and forget it.