Water flow - more through 45 elbows than 90 elbows?

[trader4]

They quote the flow restriction of the various fittings by the amount of equivalent pipe length they add. And while the 45s are individually about 5x less restrictive, you do need to then use two of them and the net effect in the given application isn't enough to make any noticeable difference. For example, a 1/2" 90deg elbow is equivalent to 3.6 feet of pipe. A 1/2" long radius 90 is equiv to

2.2 feet. A regular 45 elbow is .7 feet.

So, using two 45's, you get 1.4 feet versus 3.6 feet, saving equivalent to 2.2 feet of additional pipe run. If you used a long radius 90 elbow, you'd only be saving .8 feet of equiv pipe.

Those numbers were for screwed fittings, but similar effects are going to apply to copper as well.

[EXT]

Personally, I always use a 45 degree elbow when I have a choice. For example to change directions and elevations at the same location, such as when a pipe is traveling parallel to and between joists and must make a 90 degree turn and drop below the joists, I always use the 45 to angle down to below the joist and then a 90 to turn across the bottom of the joist. If I am going around something such as another pipe where one would need 4 90s to get around the obstruction, I always use 4 45s to accomplish it, if the obstruction is only slight, I will try to use "street" 45s to accomplish the offset. To me it looks better, it does improve the water low and also reduces noise at a high water flow.

[Zootal]

"EXT" wrote in news:4b742d57$0$77551$ [e-mail]:

Ah, there is something I hadn't thought of. How much more likely are the pipes to hammer because of 90 degree elbows, versus 45? I would bet that

45's are quite unlikely to cause hammering problems. though two 45's in a row might hammer just the same as a 90. Just guessing - I'm way outside of my area of expertise here. I don't want to do plumbing long enough to actually get good at it :-P

[hrhofmann]

But the OP said 2-90's or two 45's

[Phisherman]

There are several factors that help or hinder water flow. The area of study is called "fluidics" and often taught in mechanical engineering courses. For home plumbing, it probably doesn't matter if you use 45 or 90 degree elbows. I prefer the 90-degree bend and only use the 45-degree elbow if required.

[Stormin Mormon]

Long radius 90 have less resistance, though I'm not sure if they are made.

[trader4]

Yes, I missed that he was considering two 90's, because in many cases you would use one 90 or two 45s to achieve the same direction change. So re-doing the math, he's save about 6 ft equivalent of pipe. Which means all other things being equal, I'd use the two 45's.

[DerbyDad03]

If 45's are less restrictive than 90's, then the smooth curves of Pex must be even better.

[DD_BobK]

SM-

They are still made (long sweep copper tube elbows) & are available (at a minimum) at McMaster.

When I wonder if something is "available", I use McMaster as an "existence check". If McMaster has it, it's got to be available elsewhere as well, probably for less. If I'm in a hurry or dont want to research another source, I buy it from McMaster.

Pay with a CC and purchase before noon, I can have it before end of business that day or early the next day.

I used to say......... "if it ain't in the McMaster catalog, it probably doesn't exist and you probably don't need it anyway."

cheers Bob

[Stormin Mormon]

Thank you for your kind wisdom. Isn't that like Ralphs Pretty Good Grocery. I heard that on Prarie Home Companion, years ago. I seldom listen to NPR (National Liberal Radio). But it was on, the one time I was visiting my Dad.

[Doug Miller]

When are you going to fix your newsreader configuration so it puts your sig at the bottom where it belongs?

[Twayne]

Not likely to make any difference, I don't think. Hammering is more the effect of quickly turning a faucet off quickly which lets the water's inertia try to move the whole pipe system and thus "hammers". If anything,

90 would improve it by adding some damping or slowing to the "hammer" action.

HTH,

Twayne

[Twayne]

As long as the end-of-the-line is short in distance and smaller in diameter than the source up to that point, it's always going to be fine unless something odd comes into play. And especially if you leave the lo-flow restrictor in place - heck, you could probably feed that with 1/4" pipe! Personally, first thing I do with a shower is remove the restrictor especially if it's one of the temperature-monitoring non-scald types, which is about all you can buy today. I love that constant temp setting; let them flush the toilet and run the washer; all I see is a difference in water pressure but no temp changes of more than barely noticeable.

HTH,

Twayne