[Pollard]

Looks like it’s commonly used as a hydraulic fitting but probably used for a lot of things.

Here’s some with the cheapest being $7.49 - free shipping - https://www.ebay.com/sch/i.html?_nkw=6806-06-04&_sacat=0&LH_PrefLoc=1&_sop=15

Tried a few different titles base on that list but the above is always the cheapest. 6806-06-04 seems to be a Brennan part #.

When I was buying for the maintenance dept at my last job, I stumbled across many of those fittings with the oring and there are a few different types that are all similar.

Yep, $7.49 on ebay or $7/80 on amazon. Choose your pick.

[Paul R.]

Thanks - The eBay listing doesn’t detail what the material is (probably steel) so I messaged the seller to ask about it.

While I was at it I asked if they’d ever seen the same thing but with a barb for a 1/4” ID air hose on the present NPT side. A shot in the dark.

[Paul R.]

Heh, with the better rebate I get (through June) on the credit card I would use for Amazon. I would come out all of 8 cents cheaper on Amazon. And probably easier return if needed.

I “could” probably get away with a cheaper single adaptor that goes from NPT to the barbed end, and use a little JB Weld when I thread the NPT end into the compressor, to seal things up & strengthen the attachment. The threads “just catch”. BUT, I’d be hosed if the barbed end ever got damaged.

[Paul R.]

BTW, thanks again to Pollard for the ideas / links for the disc type water filters: I’ve found various (and cheaper) permutations on Amazon and elsewhere that should help with water out to the garden and other outdoor uses.

THIS one, for example, might be well worth adapting to:

https://www.amazon.com/UPLYKKE-Strainer-Disc-Filter-Thread/dp/B0C5JYKWT4?ref_=ast_sto_dp

or compromising a little, perhaps:

https://www.amazon.com/UPLYKKE-Irrigation-Strainer-Disc-Filter/dp/B0CR1NH2LC?ref_=ast_sto_dp

Curiously enough, the first use of these disc type filters for irrigation was in Israel.(1)

However, it turned out to be unexpectedly difficult to get reasonable price disc filtering down to 30 microns, for the house, and Wikipedia weighs in too, stating the minimum is usually 25 microns.(1) It also turns out these filters clog more rapidly than other types when “organic” matter is the problem(1) — evidently they are almost too effective. Indeed, tiny cellulose fibers are our biggest problem in our house water supply - they clog the fine screens in faucets and esp. the inlets in the back of the clothes washer...

I don’t know how filter area is even calculated for the variable density foam type filter elements that we have been using recently. The disc filter unit linked above is stated to have a filter surface area of 525cm2. That sounds impressive, but, images of 10” x 2.5” pleated polypropylene filter elements show them to have around 50 pleats. A good guesstimate for the surface area of each pleat would be (converting to metric) about (2.5 x 10) x (2.5 x 1.5) ≈ 94 cm2. 50 pleats gives you 4,700 cm2 of filter area. :-)

So... I think that for the house water supply line I am going to stick with our existing filter housing and try using these washable pleated polypropylene media cartridges, buying in bulk:

https://www.amazon.com/gp/product/B07Y28N3GM/ref=ox_sc_act_title_5?smid=A2TUU5W2X2HHE7