Reaming or tapering copper pipe?

Having read about the damage that turbulence can do to copper piping and the importance of reaming and cleaning, I wonder why instead of merely making the inside bore smooth we don't taper it?

If it's not tapered, water will encounter a 'cliff' approximately equal to the pipe's wall thickness (minus any shoulder inside the fitting, assuming there is one and the pipe was cut square and snugged up against it.)

Most of the reaming tools do a bit of tapering.
However, the fitting is recessed, so for the most part, even if it were straight cut, it would go by rather easily.

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DonL

If the piping is installed properly, it will be sized so the flow velocity is NOT high enough to cause "turbulence". I have not had any copper tubing installations fail because of erosion, other than when a circulation pump is installed and the flow is NOT modulated to the amount necessary for proper operation.

DonL said:

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DonL

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DonL, speaking as a real rocket scientist - I worked on the F1 Apollo first stage - I'd not be asking about reaming copper tubing for my rocket motor.

hj, you probably meant to say "I have not had any copper tubing installations fail because of erosion ... that I'm aware of, yet ..."

I believe that you need to stay around 2 ft/sec (and no interior disturbances to flow) to be reasonably certain of no turbulence, so no half-inch anywhere in your plans, and three-quarter type L is good only for only about 3 GPM.

The working compromise seems to be 5 ft/sec for hot, 8 ft/sec for cold, at which point it appears you have to either be very careful or not worry about it - it'll take decades to eat through. Which is why I was asking.

http://www.copper.org/applications/plumbing/techcorner/designing_piping_systems.html

quote; I have not had any copper tubing installations fail because of erosion ... that I'm aware of, yet

I meant what I said. In 60+ years of plumbing, the ONLY INTERNAL erosion I have encountered has been from oversized hot water circulation pumps which move the water too rapidly. AND that erosion almost always occurs at or just after elbows, not in straight sections such as through tees, etc, nor due to "unreamed" copper tubing.

Not to be argumentative but unless you've had occasion to pull out some of your sixty-year-old work and slice it open you have only a gut feel that it's okay. The guy in the lab coat did that and produced a fairly scary picture which for my own work I plan to believe.

It might turn out that in 1950 all the copper produced was type K or thicker - copper wasn't particularly expensive then - and in fact your pipes and parts are clean as a whistle, or you routinely still use K with walls that more than make up for the slightly increased velocity, or you always install one size bigger than is commonly done, or the water in your community is especially kind to copper. I don't know.

And of course the 'low velocity' warning is right on the mark, and there's at least one study that suggests 5 fps is okay if you're careful with cleanliness and turns, but I'm afraid that people will take your advice and say to themselves "I haven't heard of any pinholes in my work either, so I must be doing it right" which for whatever reason doesn't seem as certain as it used to be. All those pipes and connectors still being made in the good ol' USA?

But wtfdik? I'm new here.

In the Seattle area we have good water. I've seen some pretty old copper pipes.
However, they did make the switch away from acidic flux and now we use water based flux. There could be some issues down the road, and there have been some reports of problems at the fittings.

Some water in California is very hard on copper. I'm surprised it took them so long to go to PEX with the corroison problem there.

When I use the flip out on my tubing cutter, it puts an angle on the pipe. That's not enough for you?
If you don't ream the ends, it bends inward.