Gender inequality

At plbg.com, an interesting situation. jmoody76 says:

I'm looking for advice on what I need to go from a 1 1/2" PVC pipe to a garden hose. I found [www.plumbingsupply.com] and was looking at all the fittings but I'm not sure what combination to get or maybe there is a different way to go about this. Thanks.

Steve says use one of these:

1½ coupling or fitting with a reducing bushing

and then, he says, use

a brass fitting or hose bib, MPT x garden hose thread screwed into the bushing

[MPT = Male Pipe Thread]

In the next comment, packy says go with the hose bib:

screw one of these into the PVC adapter.

Yeah. Why didn't I think of that? The hose bib has pipe thread at the inlet end and garden hose thread at the outlet end. And it has a shut-off. And it's brass, which is always nice.

hj then replies to steve:

quote; screw one of these into the PVC adapter.

And have a few more PVC female adapters on hand so you can replace it when the male metal thread cracks the female adapter.

Ah, it's the PVC-screwing-onto-metal problem, again. This has come up before. Maybe the metal expands more from heat than the PVC does. So on a sunny day the PVC fitting may break and mess you up.

Mr leak says

Sarcasm aside
you need to know that fittings as you show i.e the pvc threaded female is not to be used Reason: the fitting will likely break Not to code
Male threaded plastic into female metal is ok
Think about the reason and it becomes clear

Steve adds:

I've never seen it in the California Plumbing Code, but it is in the California Mechanical Code.
"309.5 Plastic Fittings. Female PVC screwed fittings shall be used with plastic male fittings and plastic male threads only."

Okay. That's the idea. When I read something like that, it sticks in my head forever. I can come back in 6 months or a year and talk about it like it was part of the same conversation. Politics? Nah. Current events? Nah. Sarcasm and unfinished thoughts? Yep.

Anyhoo, I now have a better answer to that problem. In part, it comes from the same PlumbingSupply.com site that jmoody76 was using, at the Frequently Asked Questions page:

Q: "I've had a few female adapters break. What am I doing wrong?"

A: Many codes (such as UPC 1994 sec606.2.2) prohibit female PVC screwed fittings for water piping. The reason for this is pressure is exerted outwardly and eventually a female adapter can crack. We always recommend instead using PVC male adapters with metal female fittings. Specialty female threaded transition adapters, incorporating a reinforced outer stainless steel retaining ring, can help reduce problems associated with over-tightening, outward stress, etc. and may help provide a strong, leak-tight seal for plastic-to-metal transitions. Note that in some codes even these reinforced female threaded fittings are not accepted as well.

That's useful. It provides enough of an answer that I can continue designing my hose stuff and not be stopped cold by things I thought I knew, but didn't.

PS, Pipe threads are tapered so when you tighten the connection it's like a wedge creating pressure on both pieces. Under that kind of pressure, the outer piece is more likely to break.