Allowable loss in UPVC pipes

Loss of what? What forms the basis for your question and why do you not think that "zero" would not be the answer to both questions?

If your pipeline is leaking, FIX IT !

when i said loss i mean water Absorption, for example i know that when we do water test for upvc pipeline 400mm.

1 .fill the pipeline with water after close all opens

2.wait for 4 hourse to out all air , make mark on on the level of water.

3.after 30 minutes test the level of water

4.the allowalbe loss (Absorption) of water is 120mm for each 100m pipeline.

"4.the allowalbe loss (Absorption) of water is 120mm for each 100m pipeline."

Now I'm completely confused. How much water is there in 120mm? 120 mm is a linear measurement. Water loss would be in cc/ml/pint/quart/gallon or some other unit of volume.

Houston, we have a language problem.

Apparently you did not understand the replies to your first-time question. The replies were in good, first class English. And so I repeat... in our technology codes, pipeline leakage is not permitted, there is no such thing as "allowable leakage loss." Voila. But I begin to suspect that here is a language barrier... perhaps you speak of pipeline friction losses. Are you?? Yes, there is such a thing as friction losses but that's not leakage losses. Would it be too much to ask of you to describe your problem in a clear and technically precise fashion.

A pressure drop of 120mm ("head") per 100m of pipeline length would be reasonable, so I think it is friction loss (pressure), rather than leakage loss (volume), that the OP is asking about.

For liquids, the Darcy-Weisbach formula is suitable.

None of us are mind readers or have crystal balls. At least I assume so. I don't. Leakage is not absorption and absorption is not leakage. Yes, PVC does absorb water. The rate of absorption, I believe, is 0.05 % for 24 hours at 25degC or thereabouts. This is 5 hundreds of one per cent. But to make absolutely sure, consult ASTM D570.

"Leakage is not absorption and absorption is not leakage." For sure!

0.05% of what? Is this an ongoing process, or a one-time initial absorption?

(5 hundredths)

I did not look up ASTM D570...

the test we are talking about is leakage test done by

1-filling the pipe line(gravity) / manholes with water

2- the total amount of water added during the test to achieve this requirement shall be measured and recorded with the head of water at the required test pressure.

3-test duration is 30minutes (+-1 minute)

the test requirement is satisfied if the amount of water added is not more than 0.15 L/m2 during 30 minutes

ref BS 1610-1997

That definitely clarifies matters, but still seems poorly defined. I suspect that "0.15 L/m2" means 0.15 liters per square meter of pipe cross section, but I can't be sure unless it is specified so. Even if that assumption is correct, is the m2 the area of the pipe or the area of the fill point? In any case there is no reference to the length of the pipe, nor to any difference in height (and therefore pressure) between the ends of the pipe. An amount of leakage that would be perfectly acceptable for (say) a 10 km section of Ø30 cm pipe with a height difference of 100m, would be unacceptable for 100 m of Ø3 cm horizontal pipe.

Finally I saw no reference to temperature. It sounds like you have just filled a newly constructed section of pipe with water. It would be quite logical to test the pipe before the trenches were filled. In that case it is not likely that the pipe and water will be at the same temperature. depending on the weather at the time, the time of day, and the source of the water, there could be considerable temperature difference. Plastic pipe is a poor conductor of heat, so transfer of heat into or out of the water will be slow, but for a large pipe with a small fill point, one could expect to see considerable expansion/contraction, and this could appear to be leakage when in fact there is none, or vice versa.

Thanks for clarifying. My earlier mention of friction loss and Darcy-Weisbach does not pertain to the leakage question.

If this is a storm drain (and maybe even a sewer), some small leakage may be acceptable. I don't know whether the allowable leakage is calculated by formula, or heuristically based, or even somewhat arbitrary.

One thing that could complicate such a test would be correcting for the temperature of the water used for the test.