Spinwelding Water Tank


New member
Hey All,

So I foolishly ordered a freshwater holding tank and botched my fitting location. Now I'm in need of installing a new fitting on a different side of the tank. The easiest way I can think to do this is find a shop locally that will spin-weld on a new fitting in a location that works for my build, however I haven'd had any luck. I went to the local RV service shop and they said they didn't have the tool for it. Has anyone had any luck finding a shop that will do spin weld fittings on HDPE freshwater tanks? I feel like a rotomolding shop might work, too, but I haven't managed to find one. I'm in the bay area, for reference.

Other option is to install an access cover on the top of the tank which will then let me install a bulkhead fitting. This route would be fine, but it's more work and expense and adds more possible leakage points to the tank.


Engineer In Residence
If you are patient, you can hot-air weld the fitting. You will need compatible HDPE welding rods, and a hot air welder (Harbor freight has them). There are some photos in my build thread of the fittings I welded on. Its not foolproof though.

Spin welding its not difficult, you will need a 1/2"hp or so router, and a tool that works for your fitting. You can possibly make a tool using a socket and rod, or by using some wood plugs and a drill/driver bit as the shaft.


Active member
In the semiconductor equipment industry they use what are called "wet sinks" made from various plastics. (in case you are curious, these are used to acid wash the silicon wafers)

Depending on where you live, their might be a shop around.

They can weld / join just about any plastic that can be physically bonded.


I have spin-weld on fixtures to my solid rotomolded water tanks. It isn't hard, a router or angle grinder with the fitting and fitting attachment is all that is needed. I can do it for you or help you to do it yourself. You can also spin weld on a "cover plate" over the hole that is in the incorrect location to "fix" your mistake.


New member
Thanks all for the help and replies. I've already got a router that can do the spin welding, the problem is that the adapter tool to drive a 1/2" FPT fitting is around $160, which is nearly the price of a new tank with the correct fitting locations. This is why I'm trying to find a shop locally that already has the tool and is willing to do the job for me for a reasonable rate.


Van Guru
I could loan you our tool but would have to ship it.
(edit) it's for 3/4 Female NPT fittings. The ones that are proud -not flush.

We will require a deposit just in case it doesn't come back.
You'll need a router with 1/2" collet.
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2006 3500 170
There is a rotomold/watertank manufacturer over by the Stockton airport that might be able to help you out. I picked up my 5k gallon house water tank from them gave me a deal on a custom tank that was ordered and never picked up. http://www.polyprocessing.com/


FYI I have found a SF Bay Area place to get this done. Dale at S & S RV in Richmond, CA has a spin welder and some fittings. I'll know more in a couple of weeks. I'm still waiting for a blank Elkhart tank (fresh) and I have my blank PlasticWaterTanks grey already. The Elkhart comes with a kit (from RecPro) that supposedly does not need a inspection hatch and does some magic rivet nut expansion into the hole. I think spin-welding sounds safer especially for a tank inside the van.

I presume you got yours sorted three years ago?!


Active member
The Elkhart comes with a kit (from RecPro) that supposedly does not need a inspection hatch and does some magic rivet nut expansion into the hole. I think spin-welding sounds safer especially for a tank inside the van
Not only safer but all of those compression and clamp on type fittings need to sit well above the bottom floor of the tank if coming out of the side walls leaving a lot of liquid essentially inaccessible.

I am having my fresh water tank redone with spin welds from factory because I thought it would have been a good idea to just add my own fittings as needed...it wasn't.


New member
I presume you got yours sorted three years ago?!
Hah - funny to see this thread pop back up today, as I don't frequent the forum much since I'm a Transit owner these days and sold this van last year. I didn't wind up finding a spin welding solution, so thanks for putting some options out there (even if was too late to help me!).

I wound up cutting in an inspection window into the top, which let me get a bulkhead fitting in the bottom. This was a non-ideal solution because it was tricky to get the bulkhead fitting to seal properly, and I was always a bit worried with the 18" of water depth on a full tank, which would leak into the van interior if the fitting failed. I should have put the bulkhead fitting in the top with a straw reaching down to the bottom (hindsight and all...) The inspection window also made it so that I couldn't use a hose to pressure fill to overflow (getting me a FULL tank) because the inspection port wouldn't take 50 psi from a hose (or 20psi with a pressure reducer, for that matter), so I was always worried about overfilling my tank and blowing out all the fittings.

Turns out van plumbing takes a bit of work to get right! I have a much better plan for the 2nd van.

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