Pressure Testing Closed Loops

Am having problems with pressure test of new pipe. The pipe is 1250’ with most in a vertical bore (abandoned well).

The only fitting not in the basement is the factory fused ‘U’.

Am supposed to hydrostatic test at 100 psi … for the moment only have 60 psi (but this will be resolvable)

When pressurizing the pipe, the pressure gradually drops. But each time to a higher level. For example, 60 psi dropped to 15 psi in 12 hours. Then 60 psi dropped to 35 psi in 12 hours. Now it drops to 45 psi.

Is the pipe stretching or is there a small leak? Granted, the pipe ends up a little oval from being rolled at the factory and this 160 psi HDPE pipe is tough.

How do I determine if it is a leak? It would seem that any leak would not improve over time … more likely the opposite - faster/further pressure drop.

Lastly, how should such a leak be resolved? The well is not grouted at this time so it is possible to pull the pipe up … but even then, how would such a tiny leak be located?

 

The way we test HDPE is to pressure it up to 120 psi, let it it sit for an hour with an occasional boost to keep it around 120, then suddenly drop the pressure to around 60 psi.

Then watch the pressure for the next hour. The pressure should climb to some point and then stabilize. If the pressure doesn't climb or and climbs and then drops, you have a leak.

 

Great information. It does confirm the 'stretchability' of all the pipe. Naturally I hope this is what is involved ... great 'emotional' pressure to NOT pull up the pipe, lol.

Will try your test when I get something to get that high in pressure. Thought of just using air at the end (though it no longer hydrostatically tests). But there may be a funky way I can get 120 psi with what is laying around here (have a submersible pump that will go over 200 ... just a little awkward to work with. Us DIY persons sometimes have complicated lives trying to save a few thousand here and there)

 

Just pressure as high as you can then drop it 10 -20 psi, if it stabilizes, you are fine.

 

Wasn't the loop precharged from factory with air before installation. It should have hissed when cutting the ends off.

 

DIY hydrostatic tester= pressure washer. If you use the same pressure washer repeatedly you will kill it, however for your 1 or 2 tests it should be fine. A electric 1100 psi unit like from sears will fit the bill nicely. They are slow to build pressure due to volume but it works.
hope this helps
Eric

 

air test may satisfy your needs as well

 

Yes, it hissed away when cut. Of course factory charge is lower than standard operating pressures -- "Charter Geothermal coils and loops, from 3/4" through 2", are pressurized with 8 to 10 psi of air and have sealed ends. This unique feature keeps the pipe clean and helps maintain ovality during storage. When the pipe is cut on-site, you hear the air pressure being released.This is your assurance that your Charter Geothermal pipe is in perfect condition, ready to install."

Am a nervous nelly. And, Murphy-was-an-optimist. Recently a neighbor had to change the pipe in his well (after 10 years) due to it developing a pin hole. One must accept what happens, but while I'm in the test phase ... best to be thorough.


This morning dropped the pressure to 39 and within an hour it was at 40. Overall the fluctuations are less each day ... so it sounds like the pipe is just 'adjusting'. It will be a couple weeks before I bury the well completely so will observe how it goes.


Thank you all for the input. The pressure washer sounds like a good DIY tool (perhaps easier than dropping my 1 hp Brusier into a 5 gallon bucket, lol)

 

this is a good sign. If it holds, you should be good to go.

 

Sounds like it full of water already from your previous testing tryouts. If you do not have a pump to build up 100psi then use a air compressor, it will work just fine!
You just adding pressure at this point, the loop is already filled with water.

 

The pipe continues to behave the same ... pressures drops 3 psi within a couple hours, then 1 psi in 24 hours.

This morning used air compressor and got it to 80 psi (stopped at 80 because need to get a pressure gauge that goes higher). After 15 minute of adding to maintain at 80, it has been holding for 2 hours now. Really does seem like the pipe is ok. Will get a different gauge and test at 100 as per specs.

The specs are interesting:

"1E.5 (2011) Before connection (header) trenches are backfilled, heat exchangers shall be pressure tested with water at 100 psi for 1 hour with no observed drop in pressure (greater than 10 psi OR +/- 10%)"

Or course my system, being vertical, is different in that it is just a single 1/4 mile long pipe without branches. But the 'testing' requirement would seem to be the same.

Since +/- 10% within an hour is allowed, then the weird fluctuation I am experiencing is normal and not indicated of a problem -- or am I reading the specs incorrectly???

I would normally think that a leak that shows a 40 psi would really show at 80 psi.

 

It is almost certain that if you pressurize to 100 psi and watch it for an hour, it will drop more than 10 psi.

We did this today on a loop, started at 105 psi, in twenty minutes it was down to 78.

Then we maintained pressure at 100 psi for twenty minutes, dropped the pressure to 50 psi and with in 10 minutes it had climbed to 65 and held steady.

 

understand prescribed test by the code are usually industry driven.....and inspectors care little. if you called the local inspector and said "I'm doing this myself and can only get 50#" most would run with it. The inspector does not suffer the consequence of a leak.
Point is don't worry about code as much as satisfying yourself you won't have to dig anything back up.
j

 

Droping 105 to 78 in 20 minutes without a leak is amazing. It does seem that the more time that goes by under pressure, the more it stabilizes. Higher pressures seem better/quicker.

satisfying yourself you won't have to dig anything back up -- THAT is the concern.

Since there have been some posts of leaks as little as cups-per-season, I remain 'alert'. But when a leak is so small it would seem either to live with it or replace the whole thing ... how would such a hole ever be found?

Progress: Kept it at ~80 psi for a day then dropped it suddenly. It got about 57 but you could see it slowly creep up. It ended up at 62 psi last night and is the same this morning. So with no change in 12 hours, it probably is just fine. Will try to leave it for a few more days and it really shouldn't change (of which why bother with getting 100 psi gauge to fiddle some more).

Thanks for the replies

 

you can sleep peacefully at night knowing that there is not a leak

Leaks this small are mostly in a threaded joint somewhere inside.

 

Your fine.
I wouldn't be concerned if its holding for this long period of time.

 

Well, at day 3 it has dropped to 61 psi. Probably just more of the dynamics of HDPE.

Thank you for the reassurance

 

I dunno know......if it dropped 1 psi in three days, you better rip it out and do it over !!!

Is your gauge on a needle that you insert into a P/T port?

If so every time you check the pressure, you release a little water.

 

I dunno know......if it dropped 1 psi in three days, you better rip it out and do it over !!!

Yes and then it will leak 2 psi in three days, lol As they say, "Fooled me once, shame on you. Fooled me twice, shame on me"

The gauge is a permanent install. And yes it is possible for there to be leaks inside the basement, but no sign of water (or now air in the one half).

Could fill the line with LP gas which would be liquid at less than the 160 psi pipe rating. Then walk around with a blow torch... Humm, this could be useful as standard practice - when the compressor needs servicing you could have a propane furnace backup. [ more DIY dangers ]


Today it is about 59 (and 1/2 ) psi. For the next couple week I've other matters to attend to ... so will occasionally look at it (but not frequently enough to require Xanax). Am frankly sick of looking at it.

Hopefully it is just pipe dynamics. Every time I've fiddled with it in the past, the rate of drop is less.

Of course there is the "time-honored" chewing-gum-radiator fix ... just drop a pack of Wrigley's in the line and then rest in peace...

 

How much of your pipe is exposed to the air?

Temp will also affect the pressure.