When they hydro test high pressure gas cylinders they get pumped up with water to the test pressure but at the same time they measure the expansion of the tank under the test pressure. The test I watched was done by placing the test tank inside another unpressurized tank filled with water. As the test cylinder expanded it displaced some of the water in the outer tank. The displaced volume was recorded by reading a site glass affixed to the top cover of the testing tank. They were looking to see that when the when the pressure was released, the cylinder returned to its original volume (shape). and there was no peppermint deformation to that tank being tested. If the sight glass didn't return to the same starting point that indicated the tank had exceeded the elastic limits and had failed the test even though it didn't leak. Continual cycling such a thank would cause it to eventually fail.

When I was an engineer working for a major oil company we used to hydrotest pressure vessels by filling them with hydraulic fluid or light oils (diesel fuel) and compress them up with a hand-pump (similar to what you see with a small hydraulic jack). We factored in the compressibility of fluids, temperature and something known as "the steel factor". Steel does stretch under pressure and it adds a fraction of a percent to the capacity of the pressure vessel and in a failure, that steel stretch will cause an outpouring (jet, spray, stream, etc..) at the point of failure. On some of the things we tested we operated at up to 2250 PSI (on 0.375 wall thickness steel) where things were connected with ANSI 600 flanges. The pressure had to hold for twelve hours and we had to record pressure to the fraction of a PSI and temperature of the vessel. On some of these systems it was for a 30 mile long segment of pipeline that had blind flanges added at the ends (or double block-and-bleed valves). We had one notable failure on a 12" diameter pipeline that ruptured at a point where it was four feet underground. It blew a crater in the ground that looked like an artillery shell had gone off. The pressure at the end (where we were) dropped off very quickly but there still was enough dynamic energy in the system because of the steel-factor stretch.

Lol, the dog walked off into the woods for cover during the test and strolled back when it was over.

Scrapyard?! Come on Keith, no respecting southern boy would scrap that tank. It's the new BBQ smoker at the deer camp!

Very well explained . Being a boiler plant engineer safety and annual testing is paramount . Few non pros would perform a wall thickness deterioration test on an air receiver ( a good idea after 10 years ) but ya could remove the large bung plug ( most have one ) and do a visual with a borescope or drain camera .

Well Sunny beaches! I had a 80 gal tank that rusted through so I found one for 200.00 now when I was not to sure of the tank and wanted to test it. I read about people suggesting water test it, when I did not know who would do it I saw my pressure washer sitting there. After about fifteen minutes I found a quick air connector and put it on the pressure washer. iI figured maybe leave about a cubit foot of air in it and fill it with water, then I thought let’s see what KZfaq says about it. Wow found this video! Doing the same thing! God is Good!

Keith, long time lurker of your channel, here. I inherited a vintage Sears Craftsman air compressor and have been wanting to do some kind of hydro test on it just for, as another connector said, peace of mind. I didn't want to purchase any equipment that i would probably only use one, or pay to have a fully-certified test done, but as yet-another connector says, Ice seen the aftermath of a small shop compressor blow-out due to a rusty tank and I'd just feel safer with literally ANY test. I had no idea i could potentially use my little pressure washer as a pump, it never occurred to me, so thank you for that! I likely won't push the old thing over 150, I'll probably never use it for more than 80-100psi but i have over 4 decades of find memories for it and i want it to run again.

At Ball Aerospace, outside of Boulder Colorado, they had a facility that tested tanks. They were doing a repeat pressurization test, putting the tank in question through multiple cycles of pressure, and failed to realize that some of the water escaped with each venting of the tank. When the tank failed after several days of testing, the top half went through the roof and about 200 feet in the air.

i do a lot of hydro pressure testing here in the UK on check valves for the gas and oil industry when doing a test like this with large volumes of water please still take care because if you do have a failure of the tank or any of your fitting you will be surprised at the results as you can see when Keith let the pressure out at the Bottom of the tank if that had being a fitting coming off you would know about it i do pressures from 350 psi up to 15000 psi on Hydro so have plenty of experience with this type of testing it is safe but you still need to take care ENGAGE SAFETY SQUINTS and i would have put my self behind something when doing this test please do not think i am having a go at Keith but unless you witnessed a test go wrong or had one your self go wrong like i have last year when a gasket let go at 4.500 psi you then have a lot more respect for any type of pressure testing (yes i know it was only 250 psi ) but it will still hurt so take care

Having done countless hydro tests of piping systems I want to add a couple of points. First, respect pressure. All things equal it is true that the dangers of air testing far outweigh hydrotesting but dangers exist any time anything is under pressure. Second, the leak at the gauge is a great visual. Most hydrotests fail because the test apparatus leaks.

Thanks again Keith, was wondering what had happened to that tank! Good to see you are being "safe" as best you can! Enjoy your day my friend!

I'm glad I watched this before putting a used air compressor back into service! I've seen air tanks fail before with compressed air and one took off like a rocket and banged into the shop ceiling, doing lots of damage - and could have killed someone if they were standing nearby! Great job - I would never have thought of using a pressure washer to test it.

Thanks for some great and timely information. I have the exact same tank and am putting it in service after it sat a long time, now I know how to safely test it.

Thanks Keith. Very thoughtful presentation. When you brought that old compressor home I was hoping you would test the tank. Most people would have just let it rip and hope for the best.

Keith - Thanks for making this episode. I looked at my compressor which sits in a corner of the basement with air lines to my nearby work bench and the garage. Couldn't recall the last time I drained water from the tank. Even forgot I had installed a radiator petcock in the drain! So it's been a while. The water that drained out was pretty clear and less than a quart BUT that compressor was manufactured in 1970! The 2 cylinder cast iron compressor is getting pretty tired. I replaced some reeds about 5 years ago. But it's struggling again so I'm retiring the old girl. Picked up a smaller unit at (sorry!) Harbor Freight - 8 gallon vs. 20 on the old Sears BEST unit. I noticed that every compressor in the store recommends draining the tank every day after use.

Keith i appreciate your video! i have an old sears air compressor from the 70's unfortunately there is a chunk out of the crank keyway and when i contacted campbell hausfield (who made the pump for the compressor) they wanted to sell me a new pump! After that they wanted to remind me of the safety of an old tank. Now i can hydro test mine mine though i pulled the inspection plugs and looked in the tank!

This is a really great idea Keith and one I will be putting to use myself soon. Thanks for posting.

Thank you Keith! I'm looking to buy an older 360 gallon horizonal tank, and this is a great start. If it has the larger bung I'll have pros look at it, but never in my life would I have thought to use my pressure washer in this manner. I thank you for your video!

Many, many years ago a friend of my fathers walked into his body shop to find the pump and motor from his compressor setting on the floor by a large hole in the wall. Most of the tank was found in a corn field about 1/4 mile away. All of the tank peaces were never found.

When I pressure tested my old Quincy 50 gallon tank a few years back I just filled it to the top with water and put a liquid pressure gauge on it.... I then made sure all the air was out and I capped it and left it in the sun. The heat soaked tank slowly built pressure enough to successfully test it. Works great as long as you have a sunny day.

Always so pleasant and knowledgeable. Thanks for sharing. I always learn something from your videos.

thank you for the idea of using the pressure washer, I am in the middle of testing a intake manifold on a boat engine that had coolant in the oil I traced it to the intake, so before adding the oil and coolant I want to test it, thanks again

Great information Keith thanks for sharing 👍

Great way to have peace of mind that the pressure tanks is alright to use. I watched a video yesterday where a mechanic showed the aftermath from a compressed air tank failure. The shop was in disarray, with holes on the wall, & door, as well as all windows busted!

Nice easy test setup there Kieth! I imagine it would have done the full amount but it is an old tank and a test like that might cause a future failure. The thought of a tank like that exploding is pretty scary. Thanks I enjoyed the video. I'm restoring a ProAir 80 Gallon 6.5 HP 175 PSI now. It was not locked up but had some build up in the 2nd stage cylinder bore that would stop the piston a 1/2 inch from the top and not letting the piston make its full revolution. I've replaced the tank check valve, cleaned the bore to where it turns freely, replaced one capacitor and ran it with an open valve for ten minutes yesterday. I was going to do the same thing today and it popped the run cap on startup. That was a 2005 cap so I've got one ordered for it along with the oil filler breather cap. We used it for years at our Pipe Construction garage. An old tank is always sort of scary though. It is in very good shape though so I'm not to worried about the tank.

Something practical that most can do at home. Thanks Keith!

That was interesting, always wondered how I could hydrotest a tank. Thanks

Fun, in the first few second it thought, “what is that little fence on top...” 🤪

Informative video; I've had refrigerant recovery tanks "hydro-tested" for recertification, never really liked the idea of introducing water into a refrigerant tank. Now I understand the thought process of using water (safety factor) instead of another medium. Water & refrigerants shouldn't be exposed to each other, causes all sorts of problems inside a refrigeration circuit. I guess I have to trust whomever is hydrotesting the tanks properly dries the interior completely before shipping it back to me. I believe a deep vacuum pump (6 CFM or greater) drawn down to less than 100 Microns vacuum is an additional "no worries" about water inside the vessel. Good video, liked the presentation!

Thanks go the magic of TV we didn't have to wait like you did to fill that sucker up with water. It's a neat setup for testing.

Excellent explanation and demonstration.

*Tanks* for another great vid, Keith!

Good example of how to do this. Thanks, John

Tanks a million for your video , as it is good to know how to test these vessels. Cheers from John in Australia.

Nice to be here. Lance & Patrick.

Thanks for making a good education source me and my sons can get something from.... good work. 👍

I remember doing a 600psi test on a boil with a hand pump, dam it took time. But for air I do the same as you did but just use a cheep home electric one, and yes I have done a few. I also remember the day I used a pressure washer to save a 100 odd year old traction engine boiler that had both the mechanical water pump and the injector pump fail at the same time whiled heavy fired, when someone (and no not me) used a huge hose from a pump out of a dam, they pumped sludge into the tank. everyone was so worried and so I just found a quick connect and fitted it to the steam pipe and filled the boil with town water, it took a few minutes for the water to show on the gage glass but it did the job and saved the boiler, tho it needed a major clean out and retesting because of the event, but hey it worked.

Thanks for the demonstration Keith👌

Great ! It looks really professional! Maintain the good work!

You just answered all my questions in one video 😊

you're a good man keith, do enjoy your videos.

Got the same tank and I did the same hydraulic testing to over 300 PSI. I feel safe as well. Nothing like piece of mind

It would be interesting to poke a borescope inside and see what inside of the tank looks like in terms of corrosion.

Great demo!

Hi. My late Dad worked for the pumps and compressors division of a globally well known firm. He had some stories about what happens if the valve breaks off a high pressure air cylinder. The air blast from a 3,000 psi one can cut a man in half. If the tank breaks free you have a high power rocket with a mind of its own. Even at one twentyth of that pressure an air or gas cylinder air filled explosion is potentially lethal. That's why there's a 150% oveload water test. In fact, the cylinder expansion should also really be measured occasionaly as over time repeated filling and emptying will lead to fatigue failure. This is a madatory requirement for things like diver's air cylinders. Drain the tank of condensed water vapour regularly, you REALLY do not want it rusting from inside out. It's instructive to multiply the tank pressure by the inside surface area to find out the forces involved. They may suprise you. Incidentally Keith is mentioning 'pounds' a lot when he really means 'pounds per square inch'. But, it's very good of him to raise this subject. It's important. BobUK. (edit to correct my spelling).

I find these lower than tag rated home tests amusing. I've done many tank tests with old odd scrap yard or auction air, propane and other tanks I have picked up over the years and repurposed or added ports to or modified in some way and I have always done my test to 2x rated for a at minimal 10 minute hold and even done a few to 3x and 4x to push dents out. Never had one catastrophically fail either (I do stand around a corner and pressure them up remotely though) even with very rough looking air and propane tanks with build dates going way back into the 1940's!

I enjoyed your video immensely, and have a compressor tank of my own, purchased second hand, that requires testing. Thank you.For all the 13 year old 'experts' and 'keyboard kommandos' out there here is the procedure used in the fire service, their LIVES depend on compressed air tanks."Requirements For Hydrostatic Tank Testing:1. Hydrostatic tank testing must be completed by a licensed certified tank tester with special equipment designed for the task. 2. The tank should be tested every five years. 3. The tank must be tested more often than every five years if there are any visual signs of degradation or damage. 4. Requirements under the law state that the tank to be tested must be filled with water and pressurized to 167% of the maximum operating pressure listed on the side of the tank. 5. The tank, including all of the valves and other closures, must hold the pressure test for at least 30 minutes without leaking or bulging. 6. Details and requirements for hydrostatic testing are covered under OSHA regulations section 180.407."

Good thinking to do hydro testing . I did considerable amount of air-testing to failure and few can imagine the destructive ability of even a medium size vessel when the failure occurs even at rather low air pressures . It is hard to over-engineer the confinement chambers necessary to contain the "shrapnel" as the result of the ultimate failure . Most of the time even the confinement chambers are partially destroyed . Air-testing is indeed life threatening !

Great looking Golden. We lost our 'golden girl' last year.

Tanks for showing us that

That is some good info. Thank you for sharing.

That was fantastic information, thank you

That was a SOLID test.

The pressure washers I've used had a pressure gauge and pressure adjust valve. I'm a fan of cranking the valve down to zero and then back up to about the limit value I want before doing something like this, rather than bumping the wand valve on something set to 3000psi.

I love Mondays and Fridays.

The small air pocket at the top is actually useful, as that small amount of compressibility, allows the pressure to ramp-up slower. If the tank was completely full and you hit it with 3000psi, then the internal pressure would have risen very fast and it would be difficult for you to set the gauge to 225psi. :)

I've heard of this but never watched it. Thanks for this video

Good demo. Good information.

Keith you have a very humble dog that knows how to behave when there is a video cam running so he came really close to your garage house wall like " YEP I'M NOT GONNA BE IN THIS VIDEO SHOT " HE DID IT LIKE TAKING CARE OF NOT RUINING YOUR SHOT " !! HAHAHAHA AMAZING FUNNY DOG !!

Home Brew Hydro Testing using a Pressure Washer, Gotta Love It.

I love the disclaimer for the solid water remark

Good sound advice, thank you.

THANK YOU...for sharing.

I forgot who i saw do this, but a grease gun can be used to add pressure to a tank full of water. Love the channel, thanks.

Thanks for the video.

Love this!! Thankyou for sharing your knowledge??

When I was in the Air Force we did some pressure testing on some tanks about the size of yours, but we were required to go around all the welds and tap them with a ball peen hammer. It made me nervous, but when you encountered a leak it was uneventful. You just got a little wet.

well i did not think that my comment would turn in to such a bun fight. just got in from work don't know what's more dangerous high pressure testing or making a comment on You tube ! .

I had the horrible experience of being a pall bearar at a coworker's funeral. He was killed during a hydro test of a piping system. A hose broke and he was struck by water from the hose. There was a pocket of air in the pipe which added to the thrust of the water coming from the pipe. Lessons learned included included; hard piping all connections, making sure all pipes and vessels were filled 100%, using equipment intended and used exclusively for pressure testing, and keeping unauthorized personnel away from test connections. Good safety practices are required both at work and at home. Whether it be welding, cutting way wipers with a small bandsaw, pressure testing a compressed air receiver, or any other shop activity safe practices need to be followed. Bob

Hi mate, thanks for showing us how to do hidráulic test

When testing any pressure vessel in your yard OSHA requires you to utter the phrase “ here, hold my beer and video tape this “ to your buddy. If a buddy is not available then a nervous girlfriend ( a proper wife would never help you with this ) or your home security system will do and make sure your recording devices are not password protected so the internet can enjoy the results. For those with a pressure washer in their butt , this was a joke.

I'm about to do some tom foolery - but I'm glad I stumbled across this - Definitely going to give this a try to give myself some peace of mind with my repair lol.

Thank you Keith!

This was a random video picked by KZfaq Thanks I never knew how they tested Compressor tanks How do they rustproof the insides ????

Wow, Thanks, That was a great idea and I have learned a nice and safer trick. Wish this grandfather had done this test first, You can search Air Tank exploding on youtube and the explosion was caught on CCTV, The gentleman survived but was in the hospital for 2 months, Thanks again for the idea. The water would just scare the crap out of you but the air test would cut the crap out of you if it failed.

You're right about the compressibility of water. You'll experience much more flexing by the tank stretching, than by water compressing.

Valve Monky covers the essentials below Keith, it is his specialist subject, and mine. If you were doing it again; Tilt the tank till the vent is at the high spot, trapped air is your enemy. Put a positive shut off valve in circuit to hold the pressure in. Working pressure only when retesting an old unit, 200psig would be fine. Remember to test and re-calibrate the relief valve - this is actually more important than hydro testing the receiver. ... and before you test it - ding it with a hammer, and if it goes 'clunk' rather than 'clang', just scrap it.

Very well done in thank you.

Thanks Keith

If you were to measure the mid point diameter increase I wonder if it would be enough to emulate the results available from a full submersion volume increase test. I'm reminded of an interesting problem at a paint department. They had a fancy lacquer paint job on an old secondary air tank that helped to diagnose a collection of errors. In addition to their main compressor they bought a detuned to 175psi setup to provide high pressure whenever they ran their spot welder and through a series of plumbing and control mistakes over pressurized everything. This was during a rare BBQ lunch break when no one was around. A few older hoses had ruptured but the pumps managed to keep up long enough to trip a 225psi safety high pressure lock. My name was on the CSA document so I got the opportunity to sort it out, not that it matters. Their old secondary tank's lacquer paint job was full of tiny lines around the mid point indicating that cracks had formed. Everyone agreed they weren't there before. I don't know what pressure it actually shut down at but the safety switch was a fixed setting guaranteed to pop within a percentage, the new one says 2%. An old 150psi relief valve and two 200psi burst disks were pressured into accepting early retirement... with severance. An idea... A mid point diameter checking device could have a multiplier that made a dangerous increase easily noticeable or better yet detectable by a switch. You never know when a BBQ might happen.

Good test.

It is quite exciting hearing the pops, snaps and other sounds, doing a burst-test on a test-specimen. I have done that :) We pumped up the specimens to 135 bar, before they leaked, no explosion at all with water. Just a pissing little leak of clean water. Of cource, just a little little bit of air was trapped during the test. Good for 25 bar, the design that is. The test specimen destroyed. Non-destructive testing is performed at 1,33 x MAWP (Maximum Allowable Working Pressure) as I recall it, cold or @ 20°C, save for higher temperature curves according to the material properties in question.

Loved it !

Fascinating!

very good idea!

I was replacing a jammed safety relief valve on a hot water tank once. I stupidly did not release the water pressure on the unit and the damn fitting shot across the room with quite some force the moment I was done unscrewing it. It was just residential, so probably not more than 30 psi on it. I've also cut into plenty of water supply pipes while forgetting to depressurize... (seeing a pattern, eh?) When it's just water shooting at you it's just fun and giggle, like Keith says. The thing you want to be careful of is any fittings or similar coming loose for whatever reason during your test. Those could easily knock out teeth.

Compressors are no joke my brother inlaws neighbor lost his arm when the person made the mistake of dead heading a air compressor which exploded injuring 2 adults in the garage where the accident took place

I did this about 50 years ago, before homeowners had pressure washers, by filling the tank almost completely with water and then using the air compressor to pump it up to 200 psi. I doubt that I had more than a cupful of space with compressed air. No problem.

Brilliant Thanks for sharing

Good practical information Keith a little surprised about the release of pressure after the test I assume that was from a small air pocket above the pressure gauge which you mentioned in the video.

good video, thanks

Hey Keith, where did you find the quick disconnect fitting you used on the tank ?? I can't find one anywhere .

Another interesting video....thanks!

I tried to get a new tank for my 80 gal compressor. The total cost, including shipping, was about the same as a complete brand new Ingersoll-Rand 480 lb compressor. Good luck with that old tank.

For all the nervous Nellie's you need to search out "lpg cylinder burst test" (hydro pressure testing tank failure) on KZfaq You'll see how undramatic it is when these fail with water in them. They bulge a LPG cylinder out with 1200+psi.

Thanks. So interesting

Good to know .

That tank looks amazing for being 35 years old!

The quotes I have received for hydro-testing were more than the cost of a new tank. Having watched this video, I can now do my own test on my 100-year-old tank. I just have to figure out how to move that monster out of my garage. It took an engine hoist to get it in there.

One way to do this is just pump it up to max capacity with air, then set it vertically on a big pile of dry wood and then light the wood on fire. And then very quickly drive about a half mile away and try and catch it when it drops back in from orbit. I call this the maximum apogee tolerance test.