The $280 Order That Taught Me the Real Hole Saw Size for 1-1/2-Inch Pipe

The $280 order that wasn't supposed to matter

In March 2023, a two-truck plumbing contractor called our counter. He needed a handful of Charlotte Pipe PVC fittings, a few Charlotte Pipe cast iron fittings, a 10-inch aluminum pipe wrench, and a 14-inch aluminum end pipe wrench 90117. The total was $280. Our inside sales rep mouthed the word small and pointed at the quote queue. I took the order anyway.

I've been handling commercial plumbing supply orders for nine years. I've personally made—and documented—23 significant mistakes, totaling roughly $18,400 in wasted budget. Most of them came from rushing a small order because it looked simple. This one became mistake number 17.

The question that started the mess

While I was entering the line items, he asked the kind of question that sounds easy: What size hole saw for 1-1/2 pipe?

I didn't hesitate. 'One and a half inches,' I said. I was thinking about the nominal pipe size printed on the fitting. I wasn't thinking about the actual outside diameter.

He drilled the hole. The pipe wouldn't fit. He called me from the jobsite, and I could hear the saw still spinning in the background. That's a bad sound when you're on the phone with a customer.

I pulled up the Charlotte Pipe PVC DWV catalog. There it was: 1-1/2-inch PVC pipe has an outside diameter of 1.900 inches. Not 1.500. A 1-1/2-inch hole saw was never going to work. For clearance, most guys use a 2-1/8-inch hole saw for 1-1/2-inch PVC pipe. I said 1-1/2—or rather, I repeated the nominal pipe size like it was a hole size. That was the mistake.

What the catalog actually says

Per ASTM D2665 and Charlotte Pipe's PVC DWV catalog, 1-1/2-inch PVC pipe has an outside diameter of 1.900 inches—not 1.500 inches. Use the outside diameter, not the nominal size, when selecting a hole saw. Verify current dimensions in the Charlotte Pipe catalog as of April 2026.

That's the part that still bugs me. The information wasn't hidden. I just didn't check it. For 1-1/2-inch copper, the outside diameter is different. For cast iron, it can be different again. Charlotte Pipe cast iron fittings and no-hub cast iron pipe are covered by standards like ASTM A888 and CISPI 301, but you still need to check the actual product line. A 1-1/2-inch cast iron pipe is not automatically the same outside diameter as a 1-1/2-inch PVC pipe.

So the real answer to what size hole saw for 1 1/2 pipe isn't one number. It's a process: identify the material, look up the outside diameter, add clearance for the hole, and check the wall or plate you're drilling through. For common 1-1/2-inch PVC DWV, a 2-1/8-inch hole saw is a practical starting point. But I don't tell customers that without asking what pipe they're actually running.

The second near-miss: cast iron to PVC

The hole saw was the obvious problem. The bigger save came when I reviewed the rest of the order.

He had Charlotte Pipe PVC fittings and Charlotte Pipe cast iron fittings on the same ticket. That's normal at a transition, but it's also where small orders go wrong. I called him back and asked what he was connecting. He said he was tying PVC DWV into existing cast iron no-hub at a remodel. He had the PVC fittings and the cast iron fittings, but he didn't have the shielded transition coupling. He was about to make the connection with parts that looked close enough.

I'm not a code official, so I can't speak to what your local inspector will approve. What I can tell you from a supply counter perspective is this: transitions between PVC and cast iron are not a place to guess. We sent the correct coupling with the replacement hole saw. He finished the job. I added a transition check to our pre-review list.

What I changed after that day

That $280 order cost us about $180 in overnight freight, a replacement hole saw, and an hour of the contractor's time. It also cost me some credibility. But it changed how we handle small orders.

• Nominal size is not outside diameter. For 1-1/2-inch PVC, OD is 1.900 inches. For other materials, look it up. Don't answer from memory.
• Ask what the pipe is passing through. A hole saw that fits the pipe may not fit the stud, joist, or plate. Check local code before drilling structural members.
• Review transitions. PVC to cast iron, PVC to ABS, no-hub to hub—each has its own coupling and gasket requirements. Verify the Charlotte Pipe cast iron fittings and PVC fittings are compatible with the intended connection.
• Treat small orders like auditions. A $280 ticket is not a $280 relationship. It's a test. The contractor who feels respected on a small order is the one who calls you for the $20,000 job.

If you're ordering 1-1/2-inch pipe fittings or pipe wrenches

Here's the short version. For 1-1/2-inch PVC DWV pipe, measure or look up the outside diameter—usually 1.900 inches—and use a 2-1/8-inch hole saw for typical clearance. For cast iron, check the Charlotte Pipe cast iron fittings catalog or measure the pipe itself. For copper, PEX, or CPVC, the OD is different again. Don't assume.

For tools, the 10-inch aluminum pipe wrench is a good choice for tight spaces and small fittings. The 14-inch aluminum end pipe wrench 90117 gives you more reach without the weight of a cast iron wrench. Neither tool fixes a wrong hole. The hole saw has to match the pipe, not the label.

I've only worked with about 200 small plumbing supply orders in the Southeast. If you're doing industrial process piping or fire sprinkler work, your tolerances and code requirements may be different. That's a different world. But the core lesson holds: small orders expose process gaps. Fix the process, and the small customer might become a big one.

I still keep that $280 ticket taped inside my catalog. It's a reminder that the order you almost skipped is often the one teaching the lesson you needed.