Ask The Expert - January 2010
A Quick Fix For CPVC InstallationMax Gandy [email@example.com] writes:
I have an above-ground installation with 6” CPVC pipe, 140ºF and about 100 psi. One of the 45-degree elbows is leaking and needs to be replaced. This installation is critical and needs minimum replacement time. I’m considering pre-gluing a new section with a 45 installed, then cutting the old one out and installing the new using mechanical compression joint couplers. In addition, I’m thinking about installing pipe clamps on either side of the mechanical joint with all thread rods connecting in order to keep the pipe in the compression coupler. We’re hoping the mechanical fix will only cause the building to be down for a few hours. Is this the quickest fix? What are your thoughts?
Julius Ballanco, P.E., CPD, F-ASPE, responds:
Yes, this type of repair will work, plus it would meet the code. However, the manufacturers will tell you that the best joint for a CPVC installation is a solvent cement joint. While you may not have time for the solvent cement to set up, it still would be best for this type of repair.
Flow Reduction to Water MeterTim Keinath [firstname.lastname@example.org] writes:
There is a 3” water line feeding a school with a 1-1/2” meter. How much is flow reduced? I’m not sure how to determine this.
Julius Ballanco responds:
Flow is reduced quite a bit. It is very unusual to see that much of a reduction between the water service (outside/underground) and the water meter. The way to find out the restriction in flow is to check the water meter manufacturer’s Web site and download their data sheets. The data sheets have a flow curve that shows the pressure loss through the meter at given flows. The data sheet will also let you know where the meter tops out as the maximum flow through the meter.
PVC Leak TestingJ.R. Anderson, P.E., LEED-AP, Anderson Engineering, Germantown, TN, writes:
The architect on a project that I am the commissioning authority for has requested an interpretation of doing a more stringent leak test based on cycling the 24-hour pressure testing. The project is a school that is going to be the first in the area (and maybe the country) that will be a chilled beam project. The contractors want to use the traditional copper, but PVC is an option that works, and the architect is holding his ground. I have not done any research yet but thought this would be another approach.
Julius Ballanco responds:
The cycling pressure test for a field installation serves no useful purpose. Please understand that certain piping materials and fitting systems go through a thermocycling test to be qualified for listing purposes. The purpose of the pressure test in the field is to determine if there are any leaks in the piping system. It is not to qualify the pipe or the fittings. Therefore, a cycle test is inappropriate.
The design and specification prepared by the engineer (or architect) should take into account the proper piping materials for the installation based on their listing. This would include thermocycling tests when required for listing. I hope this assists you.
In Search of CAD DetailsStanley Brachowski [email@example.com] writes:
I am looking for two hydronic-related details in CAD. Specifically, dual-boiler control with temperature from an outside-located thermostat; and a typical piping layout of under-floor heating, with circulating pumps connected. Really hope you can help me.
John Siegenthaler, P.E., responds:
This is too broad of a description to get you something that might be of assistance. You might want to consider the schematics in the textbook Modern Hydronic Heating (2nd edition), or consider purchasing the Radiant Precision book available at www.hydronicpros.com and www.aecstore.com. Both references cover all of the information you are seeking.