Need Help With Sealing Compressor Fittings....

[Derek Arita]

So I've been having issues sealing the joints of my new compressor fittings. I've reworked just about all of the joints, first using tape, then using dope, then using tape and dope. Weird thing is, the first 2 or 3 joints out, before the ball valve, tested fine right after I did them, however they failed over the course of a few days. I'm testing the joints using dish soap and water, however it seems the soap dissolves the dope or at least it looks like it does.
Is there a best way to seal the joints? In the past, I've always used tape on joints and didn't bother testing or checking for a pressure drop. With this new 175psi, 60gal compressor, I want to be more careful about the joints. With the ball valve closed, should the tank maintain its pressure indefinitely or am I expecting too much?

[John K Jordan]

So I've been having issues sealing the joints of my new compressor fittings. I've reworked just about all of the joints, first using tape, then using dope, then using tape and dope. Weird thing is, the first 2 or 3 joints out, before the ball valve, tested fine right after I did them, however they failed over the course of a few days. I'm testing the joints using dish soap and water, however it seems the soap dissolves the dope or at least it looks like it does.
Is there a best way to seal the joints? In the past, I've always used tape on joints and didn't bother testing or checking for a pressure drop. With this new 175psi, 60gal compressor, I want to be more careful about the joints. With the ball valve closed, should the tank maintain its pressure indefinitely or am I expecting too much?

I sealed with a good quality tape. When I used sealer compound some connections leaked.

Instead of dish soap and water I always test with bubble solution, bought a gallon for $1 at the end of the summer one year. It gives better bubbles with even very tiny leaks. I use it for tires too.

If there are no external leaks and the tank still leaks down perhaps there is an internal leak. Mine holds the pressure, at least the times I checked after several days. IR 5hp dual stage 60 gal.

[Lee Schierer]

Personally, I like Loctite 565 pipe sealant with teflon. It applies easily and allows for some immediate adjustment (teflon tape does not). Properly tightened fittings will seal instantly to moderate pressures. For maximum pressure resistance and solvent resistance allow the product to cure a minimum of 24 hours.

[Mark Klosky]

I was once told by a boiler guy and union pipefitter that one of the questions on the pipefitters' licensing exam was "Teflon thread tape is an acceptable thread sealent. True or False." The correct answer is False as Teflon thread tape is considered a lubricant and not a sealant. I have stuck with that bit of knowledge for a long time, but have since come to learn that several wraps of teflon tape, applied correctly, can seal threads. I always try to buy thicker teflon tape when possible so as to stack the odds of it actually sealing the threads in my favor.

[Bill Dufour]

For NPT joints I like the teflon dope in a brushtop can. These are all NPT threads? Other types need oil and never any dope.
Bil lD.

[Tom M King]

What Pipe dope, and what tape? There are many. I used tape and dope on one 175 psi compressor, years ago, and it has never leaked since. Either by itself would not do it. That was with the thin white tape though. Since then, on other compressors, I've just used a non-setting sealant. I'd have to look to see which one it is, but can if you need me to. I don't like for them to leak either.

Did you try tightening any leaking joints any more while the bubbles were being generated?

[Derek Arita]

Tom, when I used dope only, once the joint was tight, it was physically locked, like bottomed out. With the tape and 4 or 5 layers, I suppose I could have tightened further, although I was cranked down as far as I dared. Maybe I'm just not strong enough or have enough torque on the joints.?.

[Tom M King]

Something doesn't sound right about a joint bottoming out. I would think you would be plenty strong enough with a wrench. I would try a little more while a joint is blowing bubbles though. You shouldn't have to build up a tapered thread joint like an NPT.

For my sharpening sink, a guy gave me a bunch of stainless steel pipe pieces that he had used for some beer brewing setup, that he quit bothering with. A couple of those long pipe nipples had something screwy going on the with threads. They bottomed out, and wouldn't seal. I had to take those out of the system.

I just looked out in that shop, and this is the thread sealant I used not too long ago on a 10hp, and refrigerated dryer setup, and nothing leaked after the first go.
https://www.gasoila.com/gasoila-soft-set-thread-sealant-with-ptfe.html

edited to add: I really don't think the type of pipe thread sealant should matter, or at least, not to start with. Did you give it any time to set before pressurizing the system?

[Derek Arita]

Something doesn't sound right about a joint bottoming out. I would think you would be plenty strong enough with a wrench. I would try a little more while a joint is blowing bubbles though. You shouldn't have to build up a tapered thread joint like an NPT.

For my sharpening sink, a guy gave me a bunch of stainless steel pipe pieces that he had used for some beer brewing setup, that he quit bothering with. A couple of those long pipe nipples had something screwy going on the with threads. They bottomed out, and wouldn't seal. I had to take those out of the system.

I just looked out in that shop, and this is the thread sealant I used not too long ago on a 10hp, and refrigerated dryer setup, and nothing leaked after the first go.
https://www.gasoila.com/gasoila-soft-set-thread-sealant-with-ptfe.html

edited to add: I really don't think the type of pipe thread sealant should matter, or at least, not to start with. Did you give it any time to set before pressurizing the system?
Tom...honestly, no I didn't wait. When I finished with all the connections, I pressurized the system. I didn't know I had to wait.

[Tom M King]

I was reading specs on them a little while ago, and for Rectorseal no.5, which is a pretty standard one, and one of the weaker ones, it says it's good up to 100 psi for immediate use. I think most ask you to wait 24-48 hours for high pressurization. Read the bottle of whatever you have.

[Bill Dufour]

Many of the Chinese made fittings have bad threads. You really should run a tap or die over them to clean them up before use. Sometimes British threads end up on them with no taper.
Bill D

[David Buchhauser]

Many of the Chinese made fittings have bad threads. You really should run a tap or die over them to clean them up before use. Sometimes British threads end up on them with no taper.
Bill D



https://www.youtube.com/watch?v=-yGRgv2flfs

412085
(https://www.youtube.com/watch?v=-yGRgv2flfs)

[Mike Cutler]

So I've been having issues sealing the joints of my new compressor fittings. I've reworked just about all of the joints, first using tape, then using dope, then using tape and dope. Weird thing is, the first 2 or 3 joints out, before the ball valve, tested fine right after I did them, however they failed over the course of a few days. I'm testing the joints using dish soap and water, however it seems the soap dissolves the dope or at least it looks like it does.
Is there a best way to seal the joints? In the past, I've always used tape on joints and didn't bother testing or checking for a pressure drop. With this new 175psi, 60gal compressor, I want to be more careful about the joints. With the ball valve closed, should the tank maintain its pressure indefinitely or am I expecting too much?

Derek
Dope and Teflon together are going to be problematic.
There are a zillion formulations of pipe dope and it is very important to know the properties of the dope that you are using. most of the dope in a big box store is aimed at low pressure, fluid applications. You need to seal against a higher pressure "gas" applications.
The best sealant I have found that is easily available in big box stores, is the "yellow" tape for propane and natural gas use. It has to be rated for tank pressures which are higher than what you are dealing with. I know that there must be something to it's properties other than just teflon and colored yellow, because it changes color and sticks inside the threads, unlike "white" teflon tape
Here are a few tips
-Clean all threads with lacquer thinner, or acetone. Get the old tape, dope, and machine oils out of those threads.
-Use high quality brass NPT fittings. Your tank is carbon steel, you want the fitting to be the sacraficial material and not the tank. You need fittings that are softer than the carbon steel.
- An NPT fitting should never bottom out. Something is wrong if it does. If you need to heavily wrap a fitting to "take up slop", something needs to be replaced. If this doesn't solve the problem, there are epoxy thread sealants, both liquid and solid, that can make up the slop in poorly machined, or damaged fittings.
- Soap and water is "okay", but get a bottle of leak check or "Snoop" to look for leaks.
- If your sealant has a cure time, abide by it.
- Many "fluid" sealants are an aneorobic cure. They cure in the absence of air. The sealant left outside the joint will be soft and sticky, the sealant inside will harden. Don't look at the excess material on the outside and think it is the same inside the threads.
- In industry, liquid "pipe dope" type sealants for gas applications are normally avoided. They can stay soft and eventually make it to the regulators and clog up orifices and regulator filters.
- The "bung" on the tank that you are attaching your first fitting to, does not get "cranked down". It should have an O-ring, or gasket seal. If you tighten it to much the O-ring, or soft gasket will deform and you'll get leaks.
- Yes, your tank should maintain pressure indefinitely. However, as the tank heats up and cools down with ambient conditions, the pressure inside the tank will reflect this. It's not uncommon in the winter for me to see 10psi swings in static tank pressure. My tank is kept pressurized all winter long with little to no use, and it maintains pressure. ( My tank is always left pressurized actually. )

[Derek Arita]

Mike, took some of your advice and got some yellow tape, leak finder and some stuff called True Blue...said it was for gas, among other stuff. I also got a new 3/4 nipple, just incase. I let the old made-up fittings set over night, just to see. Charged it up this morning and used the leak finder on it. Wouldn't you know, no bubbles. So, I discharged the tank and I'm going to let it set a day or two longer before I recharge the tank. Hopefully, everything stays put. I also never considered that the charged air may cool and show less pressure. Also, to throw in another wrench, the main gauge on the tank is kinda hinky and does fluctuate when I tap on it.
I did watch the vid, along with others and they were informative. One of the problems is, of course, how much do I crank down. Now I know, I shouldn't have to crank down till it locks up. Somewhere along the way, is tight enough and that's where the tape and dope should be doing the sealing...right?

[Mike Cutler]

Derek
How much to tighten a fitting is kind of subjective. I personally like to leave some "room" to take up the fitting if I need to.
A high quality, machined, NPT, fitting will probably be about three quarters to one full turn from hand tight. After that you risk stretching threads and then the fitting is toast.

[Derek Arita]

Derek
How much to tighten a fitting is kind of subjective. I personally like to leave some "room" to take up the fitting if I need to.
A high quality, machined, NPT, fitting will probably be about three quarters to one full turn from hand tight. After that you risk stretching threads and then the fitting is toast.
Mike, had no idea. I thought I had to use much more force to keep it from leaking. Can't tell you how many turns I used, I'm sure it was more than what you advised. I'll be much more aware in the future, if I need to redo any of those joints. That is exactly what I needed to know.

[Charles Lent]

I used a product called "Leak Lock" when assembling my compressed air system. It's a paste type joint compound that's available at refrigeration supply houses and on line. Even Amazon has it. I've never had it fail me. I also do refrigeration work and most other pipe sealants get eaten by the refrigerants. Leak Lock doesn't. My compressed air system gets turned off when I leave my shop, but never do I bleed off the pressure. I can come back to the shop a week later and still have almost full pressure.

Charley

[Erik Loza]

Many of the Chinese made fittings have bad threads. You really should run a tap or die over them to clean them up before use. Sometimes British threads end up on them with no taper.
Bill D

This actually happened to me recently with some fittings from the local BORG. Bought half a dozen. Five went on fine, the other seemed seemed like some entirely different thread pitch. To make sure I wasn't losing my mind, I checked the SKU and it was the same as the rest. Go figure.

Erik

[Jacob Reverb]

All you need is this:

Permatex Aviation Form-A-Gasket Sealant #3

https://www.imperialsupplies.com/thumb/400/9159.jpg

I've never had it not work. With Teflon tape, I've had trouble many times, particularly with Chicom HFT fittings.

[Jerome Stanek]

When I was plumbing anhydrous ammonia piping and tanks I used John Crane pipe dope. The pressure is very high like 450 PSI or higher and we had no leaks.

[andy bessette]

I used a product called "Leak Lock"...

This is the best product to use. And avoid cheap fittings.

[Jack Frederick]

If it is a "pipe thread" it is tapered and the purpose of the tape or dope is to lubricate the joint so the metal to metal taper can make the joint. That is from my apprenticeship 50 yrs ago. The same holds true today but there have been many formulations to pipe dope since. My view is that it was a lubricant until the marketing dept got their hands on it. I would not trust a threaded joint that was "sealed." It is best to have a clean thread and you may need a die and thread chaser to clean them up. If you are having difficulty, definitely do it. My compressor will hold air but if I leave the air blower valve on the line, it will leak down over time and the compressor will cycle a few times a day. Soap and water is fine for leak testing of air pressure. I agree that todays fittings and pipe have more issues than long ago, but we had them too. The pipe seems to have hard and soft spots. I installed a tankless water heater for my daughter last weekend and had to do a substantial gas line upgrade. Knowing I had good sharp dies I had a heck of a time not tearing a thread along the way. You may not have pipe dies so if you buy at the depot or such they usually have a threader there. Run the nipples into their die by had to clean them up and get the proper size die for your fittings.

[Lee Schierer]

If it is a "pipe thread" it is tapered and the purpose of the tape or dope is to lubricate the joint so the metal to metal taper can make the joint. That is from my apprenticeship 50 yrs ago. The same holds true today but there have been many formulations to pipe dope since. My view is that it was a lubricant until the marketing dept got their hands on it. I would not trust a threaded joint that was "sealed." It is best to have a clean thread and you may need a die and thread chaser to clean them up. If you are having difficulty, definitely do it. My compressor will hold air but if I leave the air blower valve on the line, it will leak down over time and the compressor will cycle a few times a day. Soap and water is fine for leak testing of air pressure. I agree that todays fittings and pipe have more issues than long ago, but we had them too. The pipe seems to have hard and soft spots. I installed a tankless water heater for my daughter last weekend and had to do a substantial gas line upgrade. Knowing I had good sharp dies I had a heck of a time not tearing a thread along the way. You may not have pipe dies so if you buy at the depot or such they usually have a threader there. Run the nipples into their die by had to clean them up and get the proper size die for your fittings.

The problem is that you can't always get the thread to thread seal when pipe fittings have to be at pecise orientations. Sometimes you are a half or quater turn from completely tight. That is where thread sealant comes in. If you use teflon tape and have to back off even a little you have a good chance of a leak. Liquid or paste pipe sealants are much more forgiving.

[Brian Backner]

One of my uncles was a commercial plumber/gasfitter and many years ago he shared with me his secret to avoid leaks: a product called X-pando:

https://www.mcmaster.com/x-pando-joint-compounds

It comes as a gray powder in several different formulations and is mixed with water to the consistency of peanut butter for usage. Slather it onto the male threads and make the connection to 1/2 to 3/4 turn beyond hand tight. The stuff expands as it dries to something like 10,000psi. I have never had a joint leak in the black pipe I use for compressed air in over 30 years.

Taking it apart can be fun - breaking 1/2" or 3/4" fittings require at least a 24" or 36" pipe wrench. 1" requires a 36" and preheating with a propane torch. Larger than 1" is best attempted with MAPP gas or acetylene and heating cherry red. 2" and above takes two people as well as MAPP. This is some tough stuff.

[Andrew Gibson]

I have what sounds to be a very similar compressor to yours Derek, mine is a Quincy 60 Gal that goes to 175 psi. I used plain old Pipe dope from the hardware store and did not have any leaks. I also used hardware store Brass fittings. I do use Milton QD fittings as I have never had good luck with the cheep Chinese fittings. I can leave my system pressurized and it will not leak down. I will see as much as a 15/20 PSI drop in tank pressure from hot to cold. If I get it hot and let it cool down if will drop from 175 to almost 150 but then it will stay there till the cows come home.

[Derek Arita]

Andrew, thanks. Not having much of any experience with compressed air fittings, I have to say I'm learning a lot, not the least of which is that fact that I've been over tightening all of my joints. I think that has been the issue more than anything. From this point on, if I get any more leaks, I'll be armed with a good joint sealer and I'll do my best to not over tighten. Thanks all, for your help and knowledge.

[Jack Frederick]

I have to agree with you Lee. This is especially a problem in close qtrs. The normal solution is a larger wrench, a cheater or a union. I have been using the standard yellow Rector-seal ("Seal", perhaps being the operative word) forever, but i picked up a small can of the blue crap last week having forgotten the yellow can at home. Net/net it is what works but every time I have to back off on a fitting it is that one I look at first when charging the system. Sometimes you win;)

[Derek Arita]

OK...just found more leaks! They are factory joints, I think or maybe they were done at Lowes, during assembly. Anyways, the leaks are at the mail end of the gage into the pressure switch/manifold and where the safety valve connects. Since I need to angle the gage anyways, is it ok if I put an elbow between the gage and manifold? Also, can that safety valve be switched out for a ball valve or should I just assume the valve itself is good and reseal it?https://hosting.photobucket.com/images/h151/derekarita1/0/58d58fd5-0920-4c1b-94d0-7cce63926779-original.jpg?width=1920&height=1080&fit=bounds (https://beta.photobucket.com/u/derekarita1/p/58d58fd5-0920-4c1b-94d0-7cce63926779)

[Rich Aldrich]

I use RectorSeal Blue +. I used to use RectorSeal #5. Our piping contractor keeps me up to speed as to what the professionals use. I hire the contractors, so they are good about helping us out in other ways. For those of us in process industries, this sealant is preferred because it works well and can be put into service immediately. Production people are impatient.

Teflon tape can be an issue. It should not be applied to the first threads at the end because it can break off and be carried down stream. Valves and other control components will end up damaged or jammed by the tape. It is difficult to troubleshoot the problem and identity the troublesome component.

[Jerry Bruette]

OK...just found more leaks! They are factory joints, I think or maybe they were done at Lowes, during assembly. Anyways, the leaks are at the mail end of the gage into the pressure switch/manifold and where the safety valve connects. Since I need to angle the gage anyways, is it ok if I put an elbow between the gage and manifold? Also, can that safety valve be switched out for a ball valve or should I just assume the valve itself is good and reseal it?https://hosting.photobucket.com/images/h151/derekarita1/0/58d58fd5-0920-4c1b-94d0-7cce63926779-original.jpg?width=1920&height=1080&fit=bounds (https://beta.photobucket.com/u/derekarita1/p/58d58fd5-0920-4c1b-94d0-7cce63926779)

You can put an elbow in, as long as it's rated for the pressure.
DO NOT replace the pressure relief valve with anything but another pressure relief valve of the same rating. Doing so could be a good way to blow something up.

[Jacob Reverb]

Andrew, thanks. Not having much of any experience with compressed air fittings, I have to say I'm learning a lot, not the least of which is that fact that I've been over tightening all of my joints.

FWIW, back when I used only teflon tape (not the Permatex Aviation Form-A-Gasket), I sometimes found that the joint still leaked, even after I had tightened the fitting as tight as I dared to tighten it.

When this happened, sometimes (not always, maybe not even most of the time, but sometimes) I found that if I backed-out the joint maybe 1/8 turn, sometimes that would seal it. My theory was that maybe the teflon tape, after shredding, was "jamming" between the threads when I backed out the fitting a hair.

Anyway, FWIW and YMMV and it might be worth a try if/when all else fails.

[Ole Anderson]

Following. Just picked up the Kobalt 3.4 hp 60 gallon compressor today. 175 psi. Per the reviews, the tank drain was loose. Some guy had one job...

[Derek Arita]

Following. Just picked up the Kobalt 3.4 hp 60 gallon compressor today. 175 psi. Per the reviews, the tank drain was loose. Some guy had one job...

Ole, sorry to hear that. I hope you got a good price on it...it is on sale right now. I bought mine the week before it went on sale, so they gave me the sale price. Anyways, please let us know if you had any other leaks in the system. I checked all the joints I could get to and found the gauge and safety valve leak, which I can simply reseal. Hopefully, all the other joints are good.

[Ole Anderson]

Ole, sorry to hear that. I hope you got a good price on it...it is on sale right now. I bought mine the week before it went on sale, so they gave me the sale price. Anyways, please let us know if you had any other leaks in the system. I checked all the joints I could get to and found the gauge and safety valve leak, which I can simply reseal. Hopefully, all the other joints are good. Don't see any sale pricing here, paid $549. The tank drain wasn't a big deal as I replaced the drain with a 1/4" street ell, 6" of 1/4" pipe and a ball valve. NO other obvious leaks, although I didn't bubble test everything. My big leaks were the filter in my garage which I simply removed and the drain in the brand new 1/2" regulator I purchased which I fixed by adding a second O-ring to the drain. My whole system lost about 2 psi overnight, acceptable. I used Jamar's Green Stuff pipe dope rated to 4000 psi with air.

[Derek Arita]

A couple of days ago, I resealed the two leaks I had with Permatex High Performance Thread Sealant, filled the tank with air and let it sit overnight with the tank ball valve closed. It seems to have held pressure overnight, so I think I may be good...maybe. Couldn't find any other leaks, but who knows. As long as it holds pressure to the first ball valve, I think I'm good. At least I can close the valve after use and have the tank hold pressure.

[Tom M King]

I took this picture today to show the large gauges that I bought off of ebay. Search large compressor gauge, and several choices should show up. This compressor is the one I sealed with tape, and probably just no.5 in 1991. It's been turned off for at least a couple of weeks, and has lost from 175 down to this. I bought this compressor new in 1974. It's under an open trailer shed.

[Jacob Reverb]

It's been turned off for at least a couple of weeks, and has lost from 175 down to this. I bought this compressor new in 1974. It's under an open trailer shed.

Wow, that's impressive!

[Tom M King]

It might have been with some sealant other than no.5. I really don't remember, but do remember the house I was building when I decided to stop it from leaking, and remember that I built that house in 1991. I took every fitting apart, and redid every threaded coupling.

[Derek Arita]

As the OP, I thought I'd report back. It's been a few days now and the resealed dial joints seem to be holding pressure solidly. The Permatex High Performance Sealant, along with my not over tightening, seems to have done the trick. I know I can't expect the tank to hold solid pressure forever, but if it lasts a week, I suppose I should be satisfied with that. Thanks all, for the help.