Best Sealant for Trichlor Feeder Repair

[Shocking]

Aging trichlor feeder has two pressure release valves on the cover. One of them has threads so stripped that the only fix is to plug the hole completely. What kind of goop should I use to fill in that hole? This is the most oxidation-intense locale in the whole system so I have concerns about what sealant could survive in that chemical environment.

Details: With threads deteriorated it's about a 3/8" hole now. Don't know what kind of plastic the cover is. I don't use the feeder except when a bump in CYA is needed, so its duty is limited but occasionally essential for pacifying the health inspector of this public pool. Parts for this feeder are no longer available, so the alternative is complete replacement, which is difficult to stomach ($$$) given that our primary chlorine source is not trichlor.

Thanks!!!

 

[Charlie_R]

How about using a brass bushing? Drill/tap the offending hole to the next size pipe threads, and either use a brass or PVC bushing to the size of your release valve.

 

[Shocking]

Wow, Charlie, that's a much more elegant solution than I was considering. I don't have the tapping tools, but will see if I can obtain locally. Meanwhile, I'm still open to simple sealant if one can be relied upon chemically. Thanks!

 

[Charlie_R]

.......if one can be relied upon chemically. Thanks!

Therin lies the rub.....

Some plumbing supply houses will have the proper taps, and if it's 1/8" or 1/4", major brand auto supplies sometimes carry these. you might even be able to rent for a small nominal fee.

The reason I suggested this fix is since it is for inspection purposes, all ancillary equipment normally found on this sort of thing must be in place and operable.

 

[Shocking]

Looked into the drill/tap situation. Limiting issue looks to me to be the lack of meat in that area. Photo below shows how the hole has eroded and reduced the wall thickness granted in the plastic casting. Double-checked the measurements and the hole is approximately 1/2". If next size up is 3/4", there's not enough wall thickness to drill/tap. Or is there some 1/2" item that could be inserted into the existing hole complete with some sort of permanent sealant?

 

[Charlie_R]

There are some high strength epoxies that can be used to build up the area to allow the use of the trill/tap. If you do this, be sure to rough-up the area surrounding for good adhesion. A Dremel type tool would be good for this.

 

[Richard320]

I think I'd take all the pieces to a local automotive machine shop. Look for the place that does engine rebuilding and valve jobs. Probably be run by a bunch of greasy biker types. They're used to dealing with stripped threads, and they'll have the drill press and taps and helicoils and whatever else to fix it. It doesn't cost anything to ask.

 

[Charlie_R]

Good idea, Richard! Thanks for the input!

 

[Shocking]

If I'm building up the area with epoxy, I might consider also just plugging the hole with epoxy. Sorta gets back to the question of what materials can survive this environment. If epoxy is truly legitimate than health inspector can't complain.

So I followed up on Charlie's brass fitting idea. I've learned that nominal sizes refer to inside diameter -- something I didn't know going into this. So my ~1/2" hole was originally intended for a 3/8" fitting. I've also learned that brass "plugs" (threaded, male, and intended to plug up a hole) are NOT tapered, while brass "nipples" (hollow with threaded male fittings on both ends) ARE tapered. Using the hardness of the brass itself as a sort of "tap", I've run a 3/8" nipple down into the hole, and its tapered design seems to have allowed me to tighten until a good seal is formed. I've used 3 turns of teflon tape. You can see in the pic below that I've covered the other end of the nipple with a brass "cap", also with teflon. Less than $10 in parts.

I'll install and watch for a few days and see how things go. Will let you know if there's trouble.

If this doesn't hold, I'll fall back to more elaborate solutions such as Richard proposes.

Thank you both!!!