Another pressure test question

[MrEd]

Hi all. Today maybe the day for a first fire if I can resolve a couple of last minute issues.

Question for today is, when pressure testing, how long do I need to hold air pressure, and at what pressure? I tested part of my layout yesterday at just under 30lbs of air (above that the pressure relief kept releasing air), and was able to hold close to that pressure for an hour or two (minor drop over that time period).

But this morning I come out and the pressure is basically at zero. Is air more likely to leak than water? If I can hold air for an hour or two, will that be good enough or does it basically need to maintain pressure indefinitely?

 

[sdrobertson]

Air will leak out of places that water will not. The other problem with air is that as the air becomes cooler, the pressure changes fast. What I did was fill small sections at a time with water and fixed any leak as I had them. I used quite a few shutoffs and could isolate system into manageable sections. I'm not even close to a good plumber and I learned that tight to me was definitely not tight when it came to pipe fittings! Fill with water and fix.

 

[chuck172]

Ed,
Load it with air and soap test all the joints. I saw in your pictures you used teflon tape so check real good. Bring the system to about 20 pounds- take a spray bottle with soapy water, and check each joint.

 

[steam man]

Air will find its way out of valve packings/gaskets over time. Pressure drop depends on the rate of leakage and the volume you started with. Going to zero with air does sound a little extreme. If it got colder the pressure will drop. If you are testing just piping (not a storage tank-never with air) I would go high enough to test the lowest pressure component with a somewhat safe margin, probably 60 psi. You would have to remove the relief valve and plug it temporarily, isolate expansion tanks, etc. Soap the crap out of everything. After this shakedown, I would use water at the same pressure and just wait for the leaks at threaded joints especially. An annoying drip will show up someplace. Youll need a little patience. It would be better to test thoroughly than to have the boiler in service and find that drip later.

Mike

 

[MrEd]

I'm not even close to a good plumber and I learned that tight to me was definitely not tight when it came to pipe fittings! Fill with water and fix.

I noticed that too - never having worked with black pipe I wasn't sure how tight they needed to be - real glad I use air for my first test because a lot of my joints and tiny leaks that were fixed with an extra turn on the pipes.

 

[chuck172]

Ed is using a propane tank for pressurized storage steam man, he can test through it.

 

[steam man]

Ed is using a propane tank for pressurized storage steam man, he can test through it.

I figured as much about the propane tank. I am not going to recommend on this forum that anyone use compressed gas to test a large volume modified tank at a relatively high pressure. I think this issue has been discussed here on the forum sometime ago. Sorry to be so anal. I don't want this haunting me.

Mike

 

[MrEd]

I am using a propane tank, but as of yet it is not plumbed. My tarm will come on-line before the tank, and then I'll add in the tank a week or two later.

I really am surprised at the amount of force I need to apply to these black iron pipes in order to get good seals. Almost to the point where I am afraid of breaking something (and I am using a 24" wrench). Maybe its just my inexperience with the stuff....

 

[Tony H]

I just did this piping with my nephew who is an HVAC guy and found that the 1" and larger pipes would take all I can give with a 24" wrench. I also learned that his company uses tape plus teflon dope on all fittings 1" or larger and just dope on smaller and a 12 or 18 wrench to tighten them. We ended up taking apart and redoing one section over because all I used was tape and had a couple of small drips that would only stop after adding the dope to the tape.
We tested with water and because the boiler is in a shed with a cinder block floor it was no big deal to dump a little water on the floor.
Good luck on that first fire.

 

[Couderay80]

Pressure testing with pipe. Air is elastic and can vary a pound or two. Any piping black or copper should take considerable amout of pressue and hold it indefinately. Piping only, make sure not to over inflate any non piping componets, like boiler, pressure reducing valves, and a few oter items. Piping is only as good as its threads in threaded pipe. When I check my threads including factory threads I want 3-5 turns by hand without any dope or tape (DRY). If I get more or less than 3-5 turns I cut off the threads and start over. After i check the pipe with the fitting I use rector seal #5 and coat the male threads and then put a small amount ( A-DAB) on the female fitting put the two together and tighten by hand to get my 3-5 turns then tighten with a pipewrench. Screwed joints aren't magic, you just have to make sure the threads are sharp with no knicks or missing a portion of threads for a complete seal. Been making threaded joint for over 20 years and have very,very few leaks. Again the joint is only as good as the threads and done right the leaks will stop.