Will SDR35 pipe work for penstock?

[thane]

I have looked all over the web and can't find the max psi for 4 inch or 6 inch ASTM 3034 SDR35 gasketed sewer pipe.

It's the kind of pipe that has gasketed bell ends and it's a light green color.

My site has 100 feet of head and 300 feet of run. (~43 psi)

Anybody have experience with this?

Thanks,

Thane

[chainsaw]

I used the white 4" sewer pipe with the bell ends for my hydro. I have a 300' run with only 22' of head (9.5 lbs). The PVC cement would not hold the joints together where the pipe was exposed and not buried. I ended up using short sheet metal screws and epoxy for most of the joints.

This has been ok for the last 2 years. I seem to recall that the white 4" pipe is rated for 10 lbs. of pressure(not sure). Whenever you shut down the generator, the water hammer effect is what tends to damage the(exposed) bell joints.

I don't know if the green pipe would hold more pressure than the white but I do know that the white pipe would not be satisfactory for your pressure.

 

[tanner0441]

Hi

There was a program on UK TV where they used fire hoses with a lot more than 100ft head.

Brian

[hydrosun]

I've used the four inch gasketed sewer pipe on several hydro systems. One system with a pressure of 109 psi. It's been working for 5 years without any problems with the pipe. The pipe is buried for it's entire length.

 My own system has 50 psi and I used 2000 feet of the older thinner pvc sewer pipe without pressure problems for 15 years. I did have a blockage at the end of one pipe causing a implosion  of an upper section of this weaker thin pvc pipe. But I think that kind of blockage would have hurt any kind of pipe. I've since put in a vent on the pipe after the intake on all pipelines I've installed.

So my experience shows the pipe can be used up to 100 psi. I don't know  the official pressure rating. Of course I make sure valves are closed slowly to avoid water hammer.

Chris  

[dscheckman]

Hi, I use 4" SDR 35 glued, not gasketed for about 30ft. of head and 400 ft. of penstock. All of it is above ground, in the streambed. Going on 4 years. I have had no problems. We painted the pipe for UV protection. It is surprisingly flexible, but resilient. I've worked with SDR 35 a lot and much prefer glue to gasket. The gasket can be very hard to seat. I have had issues with shut off valves at the generator, the moment you shut it off all the weight of the water above hammers the length of penstock and I think the fittings are stressed. I've not have one fail though. Good luck,

David

[thane]

Hi David,

Do you remove the gasket or glue in place?

What kind of glue... regular pvc primer and cement?

Thanks,

Thane

[dscheckman]

You can get SDR35 ( at least here in Vermont) either gasketed in 12' lengths or glue up in 10' lengths. So you don't have to modify anything, just get whichever version you decide. Regular pvc cement and primer work fine. I've been using a blue color version of PVC cement that works even when wet, which is nice for my application , since I'm working in the stream bed and its impossible to keep things dry. I also had great luck using small lengths of flexible PVC instead of fittings where the pipe turns. It makes for less friction and introduces some flexibility in the system which seems to help it weather flash floods.

David

[hydrosun]

I just leave the gasket in and use regular pvc glue as the lubricant to slide the pipe into the gasket. It doesn't have to be perfect, the gasket holds the pressure and the glue keeps the pipe from coming apart. The first time I used this pipe I took the gaskets out and had to redo one joint that I moved before the glue had set up completely.

Chris