On Tue, 11 Oct 2011 22:57:23 +0100, David Billington
wrote:

Gunner Asch wrote:
On Tue, 11 Oct 2011 06:09:12 -0700, Larry Jaques
wrote:


Why black pipe? We're not doing nat. gas here. I used all 3/4"
galv steel for my main and 3/4 x 3/4 x 1/2 tee's UP, then two 90 deg
street el's and 1/2" down to my outlet, ball valve and Q/C.

Galv flakes a lot. I hope you use a FLR on each drop, with or without
lube. F'rinstance http://goo.gl/2yi3z .

Why does the galv flake and is that inside or outside or both. I put
galv pipe handrails at my mothers place over ten years ago and the
external surface, while a bit weathered, is otherwise still perfect, I
tinned the cut ends with solder so no rust there either.

I've heard about it more than seen it. I think it's the pressure
fluctuations, plus the thread scraping during installation. That's
usually flushed out in the first water run if you use it for plumbing.
In air lines, it goes directly into the air tool or compressor intake
if not filtered.


Does remind me of my dad building some boats in the early to mid 1970s
and the local hardware stores in Huntington Long Island, NY were having
difficulty getting decent hot dipped galvanised nails, most that came in
from cheap sources you would hit and the galv would flake off at the
first strike and their days were numbered, I think they were poor hot
dip or plated. The good ones you could hammer fully home and no problems
and you could rely on them lasting.

I've had poorly plated galv nails which flaked tin all over the place.
The only clean galvanizing I've seen is on deck screws. IIRC, it's
called "micronized electroplating".


--
Fear not those who argue but those who dodge.
-- Marie Ebner von Eschenbach