Technical Blog

Recent hydraulic research on new and in-service PVC pipe has confirmed that industry-recommended flow coefficients are conservative for design of pressure and non-pressure pipes.

In piping systems, “permeation” is the movement of chemicals through a pipe wall or a gasketed joint. For potable water pipe, permeation is important because there may be adverse effects on the fluid inside the pipe.

The PVC Pipe Association has re-issued its “Tapping Guide.” The new guide includes additional diagrams and photos, as well as expanded text — all in a more logical, readable format.

Rumors have been circulating that AWWA standards allow gasketed pipe to leak. In fact, some websites for fused HDPE pipe include calculators that show huge “allowable” water-loss quantities based on this misperception.

Some engineers mistakenly contend that PVC pipe is not suitable for deep-bury projects. The misconception is that the pipe will not hold up over time under large earth loads. However, installations throughout North America have shown that PVC pipelines perform well at depths of more than 50 feet.

I sometimes hear the statement that PVC pressure pipe requires “special backfill," while ductile iron does not. This is a mind-set that is not based on engineering principles.

In 1994 AWWA’s Research Foundation published a report on PVC pipe titled “Evaluation of Polyvinyl Chloride (PVC) Pipe Performance.” We have now reached the 29th anniversary of the study – time for a look back to see if the research findings were accurate.

Water utilities have the choice of several materials for their pipe systems. For more than 70 years, PVC’s share of the municipal water market has increased steadily at the expense of iron and other pressure-pipe materials.

In 1975 AWWA published the C900 standard for PVC pressure pipe and fittings. The standard’s product sizes ranged from 4-inch through 12-inch. In 1988 a second PVC pressure pipe standard was published – this standard, AWWA C905, included sizes from 14- through 24-inch.

In trenchless installations, pipes are typically pushed or pulled into position. This pushing or pulling causes loads on the pipes that are not encountered during open-cut construction. As a result, the PVC pipe industry has developed four types of restrained-joint systems for trenchless projects.