90 degree vs 45 degree elbow. Which is best to use?

[pypeke]

I saw elbows labeled 45 degree. The elbow isn't as sharp of an angle as the 90 degree elbows. The 45s don't look like 45 degrees to me so I don't know why they are called 45 degrees.

Which would be best to use if you had to have an elbow?

http://www.poolcenter.com/p/1-5in-socket-45deg-elbow

Thanks

 

[Zrock]

Personal preference is 2 45 when I'm doing plumbing... smother flow

 

[tim5055]

I saw elbows labeled 45 degree. The elbow isn't as sharp of an angle as the 90 degree elbows. The 45s don't look like 45 degrees to me so I don't know why they are called 45 degrees.

Which would be best to use if you had to have an elbow?

http://www.poolcenter.com/p/1-5in-socket-45deg-elbow

Thanks

The one you linked to is a 45 degree. Rather than ordering on line, your local big box store Lowes/Home Depot is probably a better bet. You can buy an assortment and take back what you don't need. Just be sure to get pipe rated for pressure, not drain pipe as both come in 1.5".

 

[gonefishin]

Look for schedule 40 or schedule 80 pvc connections, which are for pressure applications.

If it says DWV don't buy it, it's for drain, waste and vent applications.

 

[JamesW]

45 degrees is how much it deviates from being straight.

The angle is 135 degrees.

More important than two 45s or one 90 is to make sure that the pipe size is big enough.

Keeping the water velocity down is key to good hydraulics.

 

[pypeke]

Thanks. I bought the 45s. Going to work on the plumbing this weekend.

I am learning so much about plumbing from this site.
Thanks,

 

[jblizzle]

I always just use 90s because the head loss difference between two 45s and one 90 is negligible in the grand scheme of things. Easier to install one fitting than 2 with small pieces of pipe in between.

And I agree that going to a 2-inch pipe instead of 1.5 as a much more significant impact than the type of fitting.

 

[pypeke]

Thanks. The pipes have to remain 1 1/2" unfortunately.

 

[jblizzle]

Why?

 

[pypeke]

The Variflow valve has 1 1/2" in/out.

- - - Updated - - -

The elbows are located in the plumbing from pump to filter

 

[jblizzle]

Well you can still use 2" if you wanted and just reduce where needed. My pump only has 1.5" fittings also, but I ran all 2" pipe and fittings on the pad.

 

[pypeke]

We only have about 18-24" between the filter and pump.

Thanks.

 

[mas985]

In Crane TP-410 manual, which I trust far more than your typical web site, the friction coefficient for a 90 is 30 while a 45 is 16 so 2 45s actually have higher head loss than a single 90. Add to that the extra glue joints which are steps, 2 45s will most certainly be worse than a single 90.

 

[pypeke]

OP here...I am only using one 45 on each.

Thanks,

 

[mas985]

1 45 on each what?

Normally when someone asks this question, it is about replacing a single 90 with two 45s otherwise it isn't the same angle bend. You can't replace a single 90 with a single 45.

 

[pypeke]

Well, my original question was.....Why is a 45 called a 45? I was thinking in math terms. Then someone explained the 45 was how far it was from being straight....not a 45° angle.

Someone else said to use two 45s. I just need a gentle curve, not a 90° to connect the flexible pvc to the variflow valve.

 

[pypeke]

Old set up with two 90° elbows on the filter in and two on the filter out. (Plumbers put the four elbows in.)

My gauge was only reading 5. We took off the two elbows on each and put on one 45 elbow on the in and one on the out of the filter. Gauge now reads 9.

So, I guess we did the right thing. All those elbows made a difference, I guess.

Hope we did the right thing. We'll see if it lasts.