Threading question

[vampress_me]

So, this has been a head-scratcher for me for a while. And this quote below is finally making me ask the dumb question.

From another post on anti-siphon valve, John posted this - “Sure, Here's the link: https://www.lowes.com/pd/Cash-Acme-B...ker/1000385647 Most Lowe's stores have them in the irrigation section of the plumbing department. This valve and two 1/2" plastic nipples and it'll connect right in place of the "self-destructing" one that was installed at the factory... Total cost, about $19 for the valve and $2 for the 2 nipples.”

Has anyone else noticed, or had the problem, that the plastic threading of fittings from Lowe’s/ Home Depot don’t work with their existing fittings in their camper? The threading is slightly different between home store fittings and camper fittings. They will screw on, but even with pipe tape, they will not quit dripping. And you can only tighten them so much. Every time I have messed with the camper plumbing, I’ve had to go to one of the camper stores that carry parts (thank goodness we have 2 independent stores with good parts sections) to find plumbing fittings that work. Drove me bonkers at first that it wasn’t just as simple as going to Lowe’s, like everyone said.

So, long post short, has anyone else had this problem, or what am I missing? It’s not like I’ve never done plumbing before either....

[JRTJH]

Lynette,

Are you talking about the white/off white CPVC fittings? I've had problems with them just like you. I try to find the black/charcoal polyethylene or plastic fittings in the irrigation department and/or at Home Depot, the plastic fittings that are in the section with the sharkbite stuff. The typical Genova 30 cent stuff in the plumbing section seldom works with PEX, at least it doesn't for me. I think part of that is the rubber pressure washer that's in all the RV fittings. It doesn't play well with CPVC stuff, just won't seal properly.

[Brentw]

Just a guess here, but there are fittings with straight cuts that are intended to seal on the pipe ( ball and socket style) and one swith a taper cut ( NPT). Could be mixing these styles.

Again.. just my guess.

[travelin texans]

Generally CPVC is a plastic pipe used mostly for hot water lines & those fittings are designed to be used with CPVC piping, same as PVC.
Your rv has PEX piping & those fittings with the rubber seals should mate up to regular NTP threaded fittings.
I've done several mods/repairs using NTP fittings, if it has the rubber seal Teflon tape is not/should not be necessary.
I'd recommend getting the Pex crimping tool & when doing any mods/repairs to tighten the Pex clamps as from my experience once you've loosened/retightened those connections the clamps are what start dripping. Just a quick squeeze with the tool & drip stops.

[srvnt]

I bypassed mine.

[vampress_me]

John, I’ve tried both areas of the plumbing section and have been left scratching my head, with leaking fittings. The camper ones are definitely not like “house” CPVC, and even the irrigation fittings I’ve tried leak.

One example is when I took out the outdoor kitchen and needed caps. Ended up buying camper caps like in the photo for our low point drains.

Another was for fixing (removing) our anti-siphon valve behind the shower. Another picture to show that. I could not get fittings that would go between the brass valve and the camper plumbing to work. So ended up with no valve for now and just a fitting in its place. Disclaimer - we never leave the black tank flush hooked up, and have a back flow preventer on the hose, which is also never used for potable water.

And there was another plumbing issue I needed to fix, but can’t remember now what it was, but again Lowe’s parts didn’t work. So I was guessing I was missing something important? But, I swear if you hold a camper threaded fitting up to a Lowe’s irrigation or PEX-y one, the threadings are different depths, for lack of a better way of saying it.

[ChuckS]

A 3/8 x 3/8 brass or steel male to male compression fitting would have worked fine on this connection. Some might be 1/2 x 1/2 male to male

Also if replacing kitchen sink faucet with residential style faucet a 3/8 male compression to 1/2 inch male NPT fitting works just fine with no leaks.


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