SDR 21 Pipe with Sch. 40 fittings? 1

[larchmont]

I received a submittal from a contractor for the domestic water system I designed on a project. I have specified 3” SDR 21 pipe per state requirements for PVC water distribution pipe under 4 inches. They have submitted PVC schedule 40 fittings for this pipe. Is this appropriate? I know that SDR 21 has a maximum of 200 psi and 3” Sch. 40 has a max of 260 psi so, intuitively, it should work, but are there SDR 21 fittings available and should they be used?

 

[bimr]

It depends on your application which you have not detailed. Is this buried pipe? What is a domestic application?

PVC SDR 21 has rubber gasketed bell and spigot flexible joints and is used for buried appliactions. For pipe larger than 1 -1/2" sise, bell and spigots joints are generally preferred.

PVC Sch 40 piping is solvent welded and not typically used for underground applications.

Additional information on the pipe:

http://www.eng-tips.com/viewthread.cfm?qid=188218&page=1

 

[larchmont]

This is for buried potable (domestic) water. Actually, I've been trying to talk to manufacturers this morning and finally reached someone at Harvel who told me that SDR 21 fittings are not made and that using the Schedule 40 for 3" fittings would work (based on pressure capacity).

However, I just turned the page in the Std. Specs and found: "All couplings installed underground to connect ductile iron or PVC pipe shall be manufactured of ductile iron". There's my answer.

Thanks for your help - ended up answering my own question.

 

[coloeng]

On the contrary, Sch. 40 solvent welded pipe and fittings is used very frequently for underground applications and has been for decades. There are numerous potable water systems, mostly rural, that use this type of pipe in much of their system. Additionally, it is one of the prime materials used for irrigation systems.

 

[bimr]

Maybe frequently, but push-on joints are the most popular joints in water distribution systems installations today. The push-on joint offers ease of installation, and when made up, the rubber ring gasket is compressed to produce water tightness, the joint permits deflections of 3 to 5 degrees, and the joints can be made in all weather conditions.