Isolation flanges

@Leon82 the swivels are handy and it emphasizes that the real sealing is done at the center of the flange where it doesn't spin whether with ring style or flat seal.

do you have the newer tacos. their shut off flanges say brass for material, but I don't know if the spinning part of the flange is brass because its painted green and I can't really get a look at the thickness profile from the side. the grundfos ones are definitely a different material on the spinning flange vs. the valve body - stainless? - and I'm looking at the pictures and maybe there is some kind of dielectric o-ring or something. brass and stainless aren't that far apart on the galvanic scale so threading brass into a stainless heat exchanger, for instance, is probably better than cast iron if wanting a threaded nipple and not adapter format right to copper (which is about the same distance anyway as brass) but they do make stainless nipples so i even wonder about approaches that mix brass and stainless. and, in the era of no lead brass (what the hell for when it comes to heating flanges and pumps?!) the premiums between brass and stainless are similar and maybe even have flipped a little although I haven't run into a completely stainless isolation valve.

indeed the conservation of the more expensive but less corrosive material means pumps (and maybe zone valves) might eventually migrate to G style unions. certainly the cheapest way to buy stainless pumps.

and then there is the question whether its not bad to have a little sacrificial iron somewhere in there that takes the brunt of the problem although it seems like (speaking of G unions) maybe they could make some sacrificial link between two brass or stainless threaded G unions with some kind of monitor for when the tubing fills up with rust and then you could throw it away and thread another one in (kind of like what we used to do with the cast iron quick fills . . . )

no question in my mind that the brass isolation flanges are miles ahead of the nonisolation steel flanges that were the bedrock of the industry for 50 [100?] years. and yet the steel flanges, when not in leaking or sweating applications were goood for 50 [100?] years . . . so a lot of this is just my typical overthinking.

maybe ditto for pump material with cast iron 007s and bosses just fine 25 years down the pike, although critical pumps or questionable water quality i'm always going to go solid brass or stainless these days.

and "I think maybe they say you can change the flange on the grundfos model isolation flanges, which i suppose could be handy if they have offerings for the odd pump that needs a different one although I have never run into that situation.

@hot_rod I totally agree re the packing nut. I put a bunch of watts isolation flanges in early in the isolation flange revolution when I repiped the system in my own house and watts was a good name stocked by a local distribution house i rely on and i didn't think about going over the engineerings of the flanges.

no 'packing nut' on these. I don't know if they have changed design but these leaked almost immediately. not continuously, thank god for small favors. cause i used threaded on the boiler side and solder style to the 3/4" loop piping. big PIA to change those.

and have to agree, going to ball valves seems like valhalla compared to the system I was working on yesterday with 2" gate valves that seem to take a half hour to close, but the systems I have with 2" ball valves I'm not entirely confident that I continue to get reliable absolute shutoff, junk carried into the seats, etc. and they do seize if not exercised. Which then gets me into the conundrum, do I want to exercise as many as I can all the time but one of them is going to get compromised in the process. then there is that belts and suspenders instinct to put in a valve so you can change the valve . . .

ok, so if that is overdone and only multiplies the exercise problem, then I wonder about pressing them on vs. threaded, because a brass valve on a copper adapter I am going to be able to change. so then the question is, is the offset standard or am i going to have to redo the piping anyway because a new isolation flange is longer (or shorter) than the old one.

and then i realize that i could have repiped a couple in the time i spent thinking about this. but, if i'm going to obsess anyway, i'm just trying to get as close to right as I can . . .