PLumbing choice: Nylon tubing & push connectors or copper & compression fittings?

I recently completed the plumbing for my on board air system using 1/2" OD copper tubing and compression fittings. I have leak-checked the system and am not happy with the frog’s breath (very fine bubbles) I see emanating from the compression fittings. The compression fittings are as tight as I can make them and there are a total of twelve of them in the system … and they all do this. The system holds pressure for about a day … steadily declining, of course. I had expected pressure loss, as most pneumatic systems leak, somewhere. This is, however, beyond what I consider acceptable.

I am contemplating removing the copper hard line and compression fittings and replacing them with 1/2" nylon tubing and push connectors from HB, but I wanted to know if anyone’s using these extensively and, if so, how well they hold pressure (i.e. how badly they leak at the connection points – presuming a perfect 90 degree cut, of course). Heat and pressure ratings would also be useful, as my front air manifold is in the engine compartment.

I’m having zero issues, by the way, at my 1/4" and 1/2" NPT connections; those are all rock solid…

Where are you using copper tubing? I ask because copper tubing is very hard to seal. Everything has to be perfect

My installation’s for a York 210L EDC with the capability to run air tools, so it’s well beyond the usual tank and valve for horns. I use copper hard line in the system:

  • Between the front air manifold and the front quick disconnect
  • Between the coalescing filter and the front air manifold
  • Between the front air manifold and the solenoid (valve)
  • Between the front and rear air manifold.
  • Between the rear air manifold and the rear quick disconnect
  • Between the twin 2.5 gallon air tanks (it’s an equalization line, as both are directly plumbed to the rear air manifold, as well – each using braided stainless over nylon pneumatic line … connected with flare fittings – no leaks on these lines)

I’d also get a little added capacity out of my line … if it didn’t leak at the fittings!

Go with the Nylon push connectors. A lot less mucking around than with metal compression fittings. I use almost exclusively all nickel plated push-in type fittings. All threads are sealed using Pirtek S69 (Loctite 545 equivalent) and everything holds 200 psi without leaking. I found that the only way they tend to leak is if you excessively twist or spin the nylon tubing once you’ve seated it in the fitting.

DBO is correct. I would go with the 1/2" air brake tubing and push fittings. Any leaks I have found in my system are on pipe threads. None of the tubing fittings leak

Any economically friendly sources for connectors and tubing rated to 200psi that you recommend?

IMPORTANT: I know and understand the difference between working and burst pressures, but I’m specifically interested in the working pressure rating being 200psi or better, as I like to plan safety overhead (at normal working pressures) into my systems and then stay below them. It’s just one of those things that gives me absolute confidence in the systems upon which I rely.

Also, I’ve not worked with these connectors or this size nylon tubing, before, so forgive me if these are dumb questions but presuming 1/2" OD tubing, what should the ID and wall thickness be for said tubing in order to utilize the push fittings? Should it be 1/2" OD, 3/8" ID and 1/16" wall thickness? If so, I’m liking this tubing (but not from this vendor; I’ve found it cheaper, elsewhere: I’m having a bit more trouble finding 200psi or better push connections, but that’s probably due to vendors listing no specs or max specs instead of working pressure specs. :frowning:

On board air systems dont typically go over 200psi.

i didn’t use any copper line or soldered joints for my 210 EDC install. its all 3/4 OD tubing and lots of brass. Also to eliminate leaky spots i would put check valves were its possible.

My relief valves (yes, plural – there’s one in each manifold) are rated at 200psi … as are my tanks… and my pressure switch is 145/170 (on/off), so I don’t expect to be near 200 psi. As I said, I like to build in overhead and work under it. :slight_smile:

I might need to ping you for York maint tips once mine’s in. I’m still waiting on the bracket fabrication. Since the engineer and machinist are doing me a favour, I can’t complain. Besides, I need to tear out all my plumbing and start anew. Meh.

add oil and forget about it… then check the filter every other week or depending on the use.

Use a oil rated hose between the filter and compressor. And lastly invest in a good coalescing filter, like Domnick-Hunter which is what i have, expensive but worth it cause trust me you dont want to be draining oil from your tanks…

Goodyear makes a 1/4 inch ID high temp oil resistant air line (blue in color) that I use for my leader line on my EDC, then it’s 1/2 inch ID air line that you can get from Home Depot, Lowe’s, Ace Hardware/Tru-Value, or any semi-truck hardware shop. I use brass 1/2 inch NPT barb fittings and double up on my hose clamps.

I do have some minor leaks, but with the EDC the refill times are roughly 30 to 70 seconds for 8 gallons of air depending on the pressure left in the tank.


What brand fittings? Also I’m noticing most come with a thread sealant on them - did you strip this and then apply your own … or was yours applied in addition to the OEM sealant … or did yours come with none?

I’ve done no mods to the York, as I’ve read mixed results from making internal changes to them. I plan on 10oz of oil but am not sure what weight to use. (Advice, please?) My coalescing filter is a Coilhose Pneumatics 8924M that I bought from KBC Tools – so hopefully it’s more than adequate. It’s got a sight glass and metal bowl, and I replaced its thumb screw with a ball valve to which I then connected a discharge hose. (I’m not going to send the discharge back to the sump with a Kilby kit like some do, as I fully expect the discharge to contain coalesced water in addition to oil.)

Thanks for all the feedback, so far. A local supply shop I’ve used for fittings, before, has great customer service, so I called them, this morning, and let them know what I was after.

They found me 100’ of 300 psi rated (with 3x burst rating) 1/2" OD reinforced nylon tubing for $37.00! Also, apparently push-to-connect fittings rated for more than the standard DOT rating (150psi) don’t often come as composite fittings, and nickel-plated fittings apparently have lower pressure ratings than all-brass fittings. I managed to wrangle up the following that meet my requirements:
1/4"MPT to 1/2"OD brass straight fitting: $3.37
1/4"MPT to 1/2"OD brass 90 degree fitting (no swivel): $7.83
1/2"MPT to 1/2"OD brass straight fitting: $8.18
1/2"MPT to 1/2"OD brass 90 degree fitting (no swivel): $9.26
1/2"MPT to 1/2"OD brass 90 degree fitting (swivel): $12.97

I wanted some 45 degree fittings but these apparently only come in composites? (None available as all-brass…) I’m going to take a count of fittings I need, place an order, and pick it up on Friday. Whee!

I almost exclusively use Parker Legris fittings (3600 series) which are are one of the best IMO. They’re rated at up to 290psi @ temps of -4 to 302 °F and designed to endure some pretty harsh environments. They do cost a bit more than the brass or nylon fittings, and are probably a bit of overkill for this application - but meh… I prefer buying quality once, instead of the cheap stuff multiple times as it breaks.

These fittings don’t have any pre-applied sealant. I’ve only ever seen that on some brass or nylon fittings. Probably OK… but I prefer to use the Loctite or S69 fluid because it’s much better stuff. If you do use a hydraulic sealing fluid on a fitting which has prior sealant applied, it’ll be best to clean off the existing stuff first, although with air it’s probably not that crucial. The hydraulic sealing fluids are designed for applications that deal with several thousand PSI - so air with a max 200psi pressure shouldn’t cause any issues if you don’t fully prep the threads.

Thanks DBO.

I was looking at the Legris 3100 series which are nickel/nylon composite fittings rated to 290 psi, but ultimately I went with what the local shop recommended (don’t know manufacturer, yet; will get specifics on Friday), as all they do is hose and fitting work.

I tend be like you and prefer quality over price. However, I’ll always take low price if I can get it without sacrificing quality. :slight_smile:

Thank you all VERY much for your input; it made a decisive difference.

I picked up all-brass push-to-connects and 300psi reinforced line on Friday. Yanked the annealed copper hard line and compression fittings on Saturday and replumbed using the new materials. I also replaced my 200psi relief valves with 235psi relief valves … and changed out the pressure switch from 145on/175off to 160on/200off. (Yup, going for more air; might as well.)

All NPT threads were sealed with Loctite 545 and allowed to cure for 24 hours. Leak testing, today, revealed no leaks anywhere that was touched by this overhaul, so I disconnected my air tanks (not part of overhaul due to difficulty to get to), unbolted and removed the tank carrier from the underside of the truck, and overhauled the tank equalization line and fittings, as well.

I’m going to pressure test the tanks and EQ line, tomorrow, after the Loctite cures … while the carrier is out of the truck. If it checks out I’ll bolt it back up and reconnect it, this week – which will leave me leak-free and waiting only on the compressor bracket. (I will, of course, use an external air source to fill up once I’m leak-free!) I never did find a suitable 150psi regulator for my horns, so I elected to go without … which will mean they’ll be louder. Darn. :wink:

Good job bud! That’s what I love about this forum, everyone here is very helpful.

Well, last week I got the air tank carrier bolted under the truck and reconnected to the rear air manifold, again. Once done I pressurized to 810KPA (117.5psi) and then checked all connections and ports with Snoop and found no leaks. (KPA was simply easier to read at the top of the liquid-filled gauge, as it was in the bubble area.) 23.5 hours later the gauge read 790KPA (114.6psi). A drop of ~3psi seems nominal, as that could easily be accounted for by a change in ambient pressure and temperature. Even if there’s a leak, it’s mighty slow … and I’m pleased with the results of the effort.

Now I just need my compressor bracket!