Intex Inflatable Spa Plumbing Caps

I’m working up to finally posting about my adventures in DIY hot tub land, but for now I’ll be brief: we have an Intex inflatable spa, and I do a LOT of DIY mods to it that require plumbing access.

Since I don’t want to drain the whole tub every time I mess with the pipes, I present: Intex PureSpa Plumbing Caps.

Blower Inlet Cap

The bubble plumbing has a check valve internally, so it won’t gush water when you unscrew it. And if it eventually leaks, the OEM pump assembly has plumbing like a dishwasher so it can’t leak into the blower motor:

Unfortunately, my OEM pump module is long since kaput and I don’t use it at all anymore, so the blower circuit is just sitting there open and unused. Even before mine started leaking, we have lots of spiders and other critters in the back yard. Maybe they’re even why it’s leaking, who knows. But it needed a cap, so I made one.

Dimensions and Assembly:

CAD model here on thangs: https://than.gs/m/1025505

I drew in CAD this plug with a 2.375″-12 thread extruded 15mm (not critical) then scaled 98.5% X/Y and 118.3% Z to match the as-measured 10.14TPI thread pitch with a decent fit. I couldn’t ever figure out what the thread is ACTUALLY supposed to be but this works. It doesn’t seem to be a standard metric OR imperial, but Intex HQ is in Long Beach CA so I suppose it’s more likely to be in inches.

Fits well, but even with ironing on the interior mating face, it doesn’t seal well enough. I bought this 1/16″ silicone gasket sheet on Amazon and cut a 58mm circle out of it to put in the bottom of my cap, and that seals it up nicely. I printed a little ring to stamp the 58mm into the sheet by stepping on it, so I’d have a template to cut with scissors.

Filter Circuit Cap

When you undo the plumbing for the filter/heater circuit, water DOES immediately start gushing. By installing these caps, you can completely remove the filter/heater/blower assembly for cleaning or whatever else, without any water leaks. You’ll need 3, one for each filter inlet and one for the return. Remove both filters and cap all 3 spots internally.

You may need to print two more for the outside ports to keep things really dry if you’re going to leave the plumbing disconnected for a long time, as the inside ones don’t seal very well (probably – I haven’t actually had a chance to test these yet).

These were drawn as 1.75″-12 thread extruded 20mm (at least, important!) and scaled 104.5% in X/Y, and 93.8% in Z to match the measured 12.79TPI thread pitch. It’s important that the thread is long enough so the TOP surface bottoms out on the inside of the hot tub wall.

Thangs link: https://than.gs/m/1025509

4 Comments

  1. Vincent
    May 14, 2024

    Hi Alex!
    I love your purespa project and I had been looking into printing a cap like this myself, but I couldnt get the threading right (I use metric system)
    Also looking to make a hose adaptor so I can use the internal pump as a vacuum to clean the thing, this cap will make that possible! 😀

    I was also wondering, since the pump has a tiny filter and is not so very efficient at filtering, if it would be possible to connect a second pump (intex pool filter) via the hole to drain the spa. cause right now I just hang both hoses over the edge, but thats not really the best solution…. Was thinking if I could connect the pump via the spa drain, so I only have to hang 1 hose over the edge.
    Also some problem there: the threading on the drain thingy doesnt fit any of our metric hose attachments sadly.

    any ideas on this?

  2. May 14, 2024

    The thread was hard! I picked a close SAE thread and just fiddled with scaling until it fit. In reality, I think most of these parts actually use NPT threads but without any taper, which is why they’re all so goofy. I’ve had much better luck grabbing NPT part models from McMaster and just using that thread, for the nearest major diameter to whatever part it is. 

    I’ve thought about doing the same to make a vacuum hose. You can see I have a weird setup with a 1000GPH intex pool pump outside the tub instead of the original filter pod, so that’d work great. But I think it’d actually be easier to just attach a hose to a big cup that fits all the way over the original filter. It wouldn’t seal very well against the side of the tub, but I bet the suction would be good enough and then you wouldn’t NEED an external filter.

    As for the third part, I personally wouldn’t use the drain hole just because there’s not a great way to seal a hose to it, but you could print some T fittings to go between the tub and the OEM filter assembly, and an extension tube for the blower. Like I said, I got rid of that entirely since we never use the bubbles and the heater died. In my case, the Y fittings allow attaching the external filter loop, as well as a loop through a propane heater in parallel. 

  3. Vincent
    May 14, 2024

    Oh well I actually screw the tiny intex filter on the water outlet when I use the inlet as a vacuum, its the same thread so the filter fits and works great actually!

    Also the drain hole in my intex greywood spa goes to a solid plastic tube, that had threads on it, and I have one (inluded with the spa) screw on part that doesnt leak and I can connect a garden hose to it, so I thought maybe if I print a simular part to go to the 1000gph filter instead of the garden hose, it might work.
    Although the T or Y part on the outside like you said, might be even smarter…
    Do you think you can help me make the model for it? Since you have the orinal exitable files.
    I use fusion 360 so I cant edit them correctly without it being chopped up xD

  4. May 14, 2024

    Oh interesting, that sounds like an improvement over mine!

    Yes – I’m away at the moment but I’ll upload those ASAP

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