Water Line psi test,

[TroyM]

Hey guys, I’m building a duplex and have a 2 inch schedule 80 PVC supply line feeding it, it’s capped at the bottom where the meter will be. During my pressure test it was pressurized with water to 75 psi, 24 hours later it was down to 70. 48 hours it was down to 61psi, and after 3 full days it’s at 55 psi.

The line is about 140 feet long and 30 inches deep. There’s sand bedding 6” below and 4” above the pipe. It’s gonna be under a paved road so we used caterpillar compaction equipment to achieve 90% compaction. I wouldn’t have expected this much psi drop. I’ve built 7 buildings over the years and plumbed them all.

I’ve had a leak detection company Investigate and so far they have not found any leaks. Tomorrow he’s gonna charge it with helium and use a sniffing device to try to find a (suspected ) leak, we used a medium body gray PVC cement and primer so I can’t imagine why a joint would’ve failed

Would you guys consider this a leak or call it good with 19 psi drop in three days

 

[Sylvan]

No leak is "good"

 

[Sponsor]

 

[Breplum]

I'd be not comfortable with that drop. I would use another gauge. I wouldn't have buried it without prior definitive testing. Sch 80 is what I would have used. Of course never use FIP PVC fittings when adapting to metal.

 

[Reach4]

The pressure test is with just water? If just water, being incompressible, I don't think you can draw inference.

If it were an air and water combination, and you had the corresponding volumes available, the calculation could be more complex.

So for example, if you had a well pressure tank added in, with say a 40 psi precharge, then a meaningful result could be computed. That calculation would include the size of the pressure tank.

 

[Sylvan]

The pressure test is with just water? If just water, being incompressible, I don't think you can draw inference.

If it were an air and water combination, and you had the corresponding volumes available, the calculation could be more complex.

So for example, if you had a well pressure tank added in, with say a 40 psi precharge, then a meaningful result could be computed. That calculation would include the size of the pressure tank.

I testified in court about a negligence case involving a general contractor who decided to test PVC with air so he could start backfilling.

The pipe actually exploded, blinding a laborer and causing permanent damage to three others.

Air and plastic piping is a no-no


As a result, testing with air pressure is prohibited by every nationally recognized manufacturer, standard, and model plumbing code authority, including:

• ASTM International
• International Plumbing and Mechanical Codes
• National Standard Plumbing Code
• OSHA
• Uniform Plumbing and Mechanical Codes

Same theroy as to why we hydrostatically test boilers and pressure vessels.

 

[Reach4]

Same theroy as to why we hydrostatically test boilers and pressure vessels.

I understand the safety aspect. But you would not just close a valve, and monitor a pressure. Instead you would have some way to measure the amount of liquid that got leaked out vs time. If monitoring a pressure with no expansion-contraction provision is really monitoring a lot of the elasticity of the piping, and the temperature change, and residual unknown-quantity air.

It seems to me that one good way would be to use a well pressure tank. Then a change in pressure would correspond to an amount of water volume change.

 

[Slomoola]

Why was it filled and compacted, prior to testing? Why not run PEX A or Copper?

 

[Jeff H Young]

if air is trapped it wont hold pressure the water soaks up the air i dont know how but you cant even get dwv to hold a head of water if its got air trapped

 

[John Gayewski]

You can't test a water line with any air in it whatsoever. It's best to fill with water, let sit fill with water, let sit, let sit, fill with water. Then test. If there is a safe way to test the line with air it's a better way, but pvc can explode when air tested. One of many reasons not to use Pvc as a water supply pipe.

 

[Reach4]

Hey guys, I’m building a duplex and have a 2 inch schedule 80 PVC supply line feeding it, it’s capped at the bottom where the meter will be. During my pressure test it was pressurized with water to 75 psi, 24 hours later it was down to 70. 48 hours it was down to 61psi, and after 3 full days it’s at 55 psi.

Does anybody think that this test produced a meaningful result that there is a problem with the piping?

 

[Sylvan]

Does anybody think that this test produced a meaningful result that there is a problem with the piping?

Yes, there is a problem

 

[Reach4]

Yes, there is a problem

If the test was as I suspect, the pressure drop could be due to a tiny increase in volume due to elastic expansion of the pipes.

So I think there is a problem with the test methodology. I do not see using schedule 80 pressure rated PVC pipe is a problem. I don't think you will find anybody recommending such a testing method.

There is a pressure test for PEX where they pre-pressurize to a higher pressure for a period, so that the PEX can pre-expand. Then they drop the pressure for the test so that the pipe is not expanding during that test. I doubt they are doing that kind of test with PVC, but if they did, they would need to pre-pressurize that to a higher pressure also.

I can no longer find that Uponor document that described the testing procedure.

So if you think that the description indicates some leak in the piping, we can disagree on that one.

 

[Jeff H Young]

in the future dont use your method of testing. its buried now just a test method there is a very good chance its all good but im not betting on it.
if you could run water through it continually and bleed the air you can hydrostatic test if there is a curb cock out there test at street pressure or bring in a water buffaloe Assuming inspector bought it off Ive always hooked up to the curb cock meter or not then if I can, I leave it hooked up indefinately during the build

 

[Reach4]

. its buried now just a test method there is a very good chance its all good but im not betting on it.

I would bet on it, as measured by what the leak detection company says. TroyM is being extra-cautious I think.

Were I devising a water test, I would consider teeing in a pressure tank or even a thermal expansion tank in place. I am not sure of the size, but I am thinking that even a 2 gallon tank would be enough.

Pressurize the air precharge to 15 pounds below the test pressure. Pressurize with water to the test pressure. Now I think that a longer term test could be run. Wait a bit for things (pipe, tank diaphragm) to creep initially, then watch for changes.

https://www.homedepot.com/p/Everbilt-2-0-Gal-Thermal-Expansion-Tank-HDET2G/330866982
https://www.menards.com/main/plumbi...det-5-m1/p-1550129344018-c-8691.htm?exp=false

 

[Jeff H Young]

I would bet on it, as measured by what the leak detection company says. TroyM is being extra-cautious I think.

Were I devising a water test, I would consider teeing in a pressure tank or even a thermal expansion tank in place. I am not sure of the size, but I am thinking that even a 2 gallon tank would be enough.

Pressurize the air precharge to 15 pounds below the test pressure. Pressurize with water to the test pressure. Now I think that a longer term test could be run. Wait a bit for things (pipe, tank diaphragm) to creep initially, then watch for changes.

https://www.homedepot.com/p/Everbilt-2-0-Gal-Thermal-Expansion-Tank-HDET2G/330866982
https://www.menards.com/main/plumbi...det-5-m1/p-1550129344018-c-8691.htm?exp=false

Im not saying its a leaker what im saying is its a inconclusive test . even no test its probebly ok .
Its his call I dont mean to be negative