Confused about Schedule 40 pipe sizes...

lyrical · Nov 22, 2015

So excuse the elementary piping question I've never had to build hard plumbing before it's always been provided for. This time I am going to attempt it.

Where my confusion is... I am going to use slip x slip fittings and the primer/glue to connect everything with pipe, unions, etc.

So... if my pipe is 1.5" would I buy a 1.5" bulkhead for it to fit inside? Same with the union... if I had a 1.5" pipe would I buy a 1.5" union, or a 1.75" union for it to fit inside?

Or if it's 1.5" pipe do you buy everything 1.5" across the board? Including couplers to fit?

Thansks

sonnus · Nov 22, 2015

If you use 1-1/2" pipe you will use all 1-1/2" fittings.

All pipe has different outside diameter compared to the nominal size. You need to forget about the actual outside diameter and just go by the nominal size when buying fittings.

lyrical · Nov 22, 2015

Thanks sonnus

You confused me with the nominal size and the chart.. but basically what you are saying is 1.5" across the board? So to connect a 1.5" pipe to a union I would want a 1.5" union? And to connect a 45 or 90 degree angle I would use a 1.5" coupler to fit inside the 1.5" pipe and 1.5" union? Sorry for the 1.5" redundancy question I just don't want to order the wrong size online.

sonnus · Nov 22, 2015

Yup, get all 1.5".

lyrical · Nov 22, 2015

Awesome ty

DaveMorris · Nov 22, 2015

You mentioned a bulkhead in your original post. You need to double check the size for it. Some of them with threads are a little off. It should follow the same thing for size, but be sure to check it.

AZDesertRat · Nov 22, 2015

Sch 40 pipe sizes go by the inside diameter where the flow is not the outside diameter which varies due to the wall thickness of the pipe. Fittings and valves are made to fit the outside diameter and take into account the wall thickness.

lyrical · Nov 23, 2015

DaveMorris said:
You mentioned a bulkhead in your original post. You need to double check the size for it. Some of them with threads are a little off. It should follow the same thing for size, but be sure to check it.

Thank you. I'm not sure how I can check it before taking it off to change it. It's what came with the tank and was already installed. I'll see what I can find out though,

lyrical · Nov 23, 2015

AZDesertRat said:
Sch 40 pipe sizes go by the inside diameter where the flow is not the outside diameter which varies due to the wall thickness of the pipe. Fittings and valves are made to fit the outside diameter and take into account the wall thickness.

Thanks! That makes sense... almost... but I am still confused. I understand a 1.5" PVC pipe is 1.5" on the inside.. but for example if I needed a coupler it would still have to be a 1.5" one correct? I'm good with the rest I think lol.

AZDesertRat · Nov 23, 2015

The first answer to you post above shows the outside diameter of various sizes of sch 40 PVC. Measure the inside diameter of the bulkhead and match it up with the chart.

Fin · Nov 23, 2015

Also, when you buy your primer, buy the clear primer. Don't use the purple stuff if you don't want your plumbing job to look messy with purple stains all over it. The dye in the purple primer is not necessary for aquarium use.