In my pool, I have two white PVC pipes that push water out, where jets are supposed to fit to increase flow rate.

The diameter of these pipes is 1.5 inches.

I purchased a 5-pack of "Pool and Spa Eyeball Jet 1.5" Threaded to 3/4" Open" jets from an online retailer.

I was sent a pack of 5 jets where the diameter of the threaded portion measured 1.75 inches, too big to fit in the 1.5" wall pipes.

I returned the pack, and requested the correct size.

Again, I was sent the same 1.75 inch pack back. The product is a Pooline item number 11211C. I found an independent description which measures the threaded portion as 1-1/2" MIPT.

Below is a photo from the website referenced above showing the MIPT, and photos of the items I received with a tape showing measurement.

Before I return these items for a third time, I want to make sure I am purchasing for the correct width. Am I simply being sent the wrong item, or am I asking for the wrong item? If so, what should I be asking for?

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Nominal pipe size is for the hole on the inside of the pipe, and that is still subject to "nominal"

A pipe which is 1-1/2 inches (actually 1.557) on the outside is a 1-1/4" pipe.

A 1-1/2 inch pipe is 1.796 inches OD.

Here's a handy and very detailed chart/diagram

You have been asking for the wrong part, and have been sent the part you asked for, twice.


In my admittedly non-plumber experience, you're being sent the correct item, you simply don't have the correct adapter. You need to get a 1.5" slip to 1.5" FPT adapter - they should be commonly available at your local big-box home improvement retailer in the plumbing section. The slip side goes on the source pipe - you can ask the store personnel about how to glue it on (it's almost ridiculously simple) and what glue you need. Take the nozzles you have with you as a CYA to make sure the adapter fits snugly when screwing them together - in the final isntallation, you may need an O-ring or thread tape of some form.

  • But why is the 1.5" threaded end actually 1.75" in diameter? It is much bigger than the pipe it is supposed to thread into. – JoshDM Jul 15 '15 at 15:14
  • It's a "standard" size measurement, not an "actual" size measurement. Very similar to the way the actual size of a "2x4" is 1.5 by 3.5 inches. – John Jul 15 '15 at 15:40
  • So what standard size measurement should I be purchasing if I want to fit the interior of a 1.5 inch threaded tube? – JoshDM Jul 15 '15 at 15:54
  • Male or female threaded end? Honestly - go talk to the plumbing department at your local big-box home improvement retailer. You're overthinking things. – John Jul 15 '15 at 16:21
  • The pipe in my pool is a 1.5 inch female threaded so I tried to purchase a 1.5 inch male threaded to go into it but I keep getting sent 1.75 inch male is there something I'm missing as to why when I request the 1.5 inch male I get 1.75 inch multiple times? – JoshDM Jul 15 '15 at 17:38

If you don't have threads, you can use what is called an "insider" or "Aussie insider" which fits smooth into the actual pipe without a female threaded adapter. They come in sizes for 1 1/2" or 2" pipe.

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