[sclindsay]

Hello, I want to install a pressure vacuum breaker (Zurn 720A) before my sprinkler system. Because of the orientation of my pipes it would be easier for me to cut the vertical metal pipe and then transition to a PVC pipe that would be the input to my PVB. I need to figure out what material the metal pipe is though. I am hoping it is copper so that I can use a SharkBite 1/2 in. Push-to-Connect PVC IPS x CTS Brass Conversion Coupling Fitting (to transition from copper to PVC). If it is galvanized steel though I wouldn’t be able to use that fitting and it would be more difficult.

My house is 80 years old so I know that galvanized steel was common then, and I’m not sure if the pipes have been replaced since then. I did just scratch the surface and the exposed metal looks orange - does that suggest copper?

Also I’m a bit confused because the Nibco elbow seems to go from the smaller vertical metal pipe to a larger horizontal 3/4 inch PVC. The elbow says 3/4 on it. Is this a fitting that changes a 1/2 inch pipe to a 3/4? I think that would be a compression fitting on the metal side and a MPT on the 3/4 end. It doesn't really matter if I am cutting the pipe anyway, just curious. Thank you for your help.

 

[Ghostmaker]

Copper pipe. Why don't you just cut out the pvc remove the pvc threaded adaptor from the brass female threaded 90. By a Brass nipple and install it with Teflon tape and pipe dope then your vacuum breaker then thread in another PVC MIP on the outlet side to adapt back to your PVC. This type of Back flow works best installed above your entire irrigation line. If your land is hilly and higher than this get a RPP Back flow with dump.
https://www.zurn.com/products/water-safety/backflow-prevention/975xl2/34-975xl2

 

[sclindsay]

Thanks for the reply. I was thinking of that way too, but then the PVB would be a bit too far along to the right to connect to the vertical PVC pipe leading down to the valves. I guess I could do it that way and then use a few elbow connectors in series to bring the line back to the left after the PVB if that makes sense.

Would you suggest not cutting the copper pipe then? Also, if I do go that route do I have it right that the copper pipe is 1/2 inch (it is definitely smaller than the PVC pipe so I think it has to be 1/2 inch) and the Nibco elbow converts it to 3/4 inch?

I should be okay with the Zurn 720A PVB that I have because my house is on top of a hill and the sprinklers will all be at least a foot below the height of the PVB.

Thanks again!

 

[Bondo]

Also, if I do go that route do I have it right that the copper pipe is 1/2 inch (it is definitely smaller than the PVC pipe so I think it has to be 1/2 inch) and the Nibco elbow converts it to 3/4 inch?

Ayuh,....... That, ^^^, is Correct,.....

 

[Ghostmaker]

Is your irrigation working fine for you with a 1/2 inch feed?

 

[sclindsay]

Yes it works fine! I have 3 zones with over 150 x 1 gallon and over 100 x 0.6 gallon drip emitters and everything seems to work well.

 

[sclindsay]

Is your irrigation working fine for you with a 1/2 inch feed?

Oh you know what I just realized?! That copper pipe size is measured differently to PVC. The copper pipe is actually 3/4 inch not 1/2 inch since the size is measured by the outside diameter. The PVC pipe looks bigger because the 3/4 inch is measure by the inside diameter (and the outside diameter is actually a little over an inch). Thank you for the comment, it made me think.

 

[Ghostmaker]

OK Cool. Can't tell pipe size by a photo thats why I took you by your word.

 

[bfrabel]

Oh you know what I just realized?! That copper pipe size is measured differently to PVC. The copper pipe is actually 3/4 inch not 1/2 inch since the size is measured by the outside diameter. The PVC pipe looks bigger because the 3/4 inch is measure by the inside diameter (and the outside diameter is actually a little over an inch). Thank you for the comment, it made me think.

Not exactly. Copper and PVC (and pretty much all other kinds of plumbing pipes) are measured by inside diameter. The PVC looks bigger because it is much thicker. The inside diameter of both pipes should be 3/4" though, or close to it. It's not exact. It's called "nominal size". Most pipes come in different thicknesses, but the OD between the different thicknesses is the same so that the fittings that are used can be interchangeable. That means that the better, thicker walled copper will have a slightly smaller inner diameter than the cheaper stuff.

The exception to the pipe sizing rules is with tubing. Tubing such as soft copper or plastic tubing is usually sold by outer diameter instead of inside diameter. This can get confusing, especially with copper, since hard copper pipe and soft copper tubing can be interchanged with each other, but you need to know how to convert the ID size to OD, and vice versa. For example, 3/4" ID copper is the same as 7/8" OD copper. A nomanaly sized 3/4" soft solder elbow or sharkbite fitting will fit the same with both (as both will actually be 7/8" OD).

Like I said, this stuff does get confusing and even screws up seasoned plumbers from time to time. Especially with the soft copper. Sometimes the stuff is marketed by it's ID size and sometimes by it's OD size, depending on the manufacturer and/or store that it comes from.

Anyways, what you have there does appear to be 3/4" I.D. copper and 3/4" I.D. PVC. If you do use a sharkbite adapter, keep in mind that it won't be secure. Sharkbite fittings are always kind of loose and able to move around. I don't know if this matters in your situation or not, but you should probably be aware of it.

 

[sclindsay]

Not exactly. Copper and PVC (and pretty much all other kinds of plumbing pipes) are measured by inside diameter. The PVC looks bigger because it is much thicker. The inside diameter of both pipes should be 3/4" though, or close to it. It's not exact. It's called "nominal size". Most pipes come in different thicknesses, but the OD between the different thicknesses is the same so that the fittings that are used can be interchangeable. That means that the better, thicker walled copper will have a slightly smaller inner diameter than the cheaper stuff.

The exception to the pipe sizing rules is with tubing. Tubing such as soft copper or plastic tubing is usually sold by outer diameter instead of inside diameter. This can get confusing, especially with copper, since hard copper pipe and soft copper tubing can be interchanged with each other, but you need to know how to convert the ID size to OD, and vice versa. For example, 3/4" ID copper is the same as 7/8" OD copper. A nomanaly sized 3/4" soft solder elbow or sharkbite fitting will fit the same with both (as both will actually be 7/8" OD).

Like I said, this stuff does get confusing and even screws up seasoned plumbers from time to time. Especially with the soft copper. Sometimes the stuff is marketed by it's ID size and sometimes by it's OD size, depending on the manufacturer and/or store that it comes from.

Anyways, what you have there does appear to be 3/4" I.D. copper and 3/4" I.D. PVC. If you do use a sharkbite adapter, keep in mind that it won't be secure. Sharkbite fittings are always kind of loose and able to move around. I don't know if this matters in your situation or not, but you should probably be aware of it.

Wow - thanks for the clarification! I measured the copper pipe and it is 7/8" OD so it is definitely 3/4" ID.

Also thank you for letting me know that Sharkbite fittings can be loose. I'm not sure if it matters for my situation. I was planning on cutting that vertical copper pipe and then using a Sharkbite adapter to transition to 3/4" PVC which will then be the input to the Pressure Vacuum Breaker (Zurn 720A). The input comes in from the bottom. Then the output comes out horizontally so I will use a 90 degree elbow and have the pipe then go down to the valve box. So I guess the Pressure Vacuum Breaker will kind of be suspended by the two vertical pipes (one of which will be the copper/sharkbite/PVC input pipe). Will this be a stable arrangement if the Sharkbite fitting is kind of loose?

Thank you.