Sucks that they are through holes. Looks like one option would be to tap for the next size up, install a stud, and then have someone run a small weld bead around the base of the new stud on the outside. The threads would take the load - the weld would just stop the leaks. Could also braze/silver solder the stud in the hole. Doesn't look like the flange would care if you opened up one of the three holes a bit to accommodate the bigger stud.

ira wrote:If it's leaking around a bolt then the drips will come from that bolt. If you set the boiler bolt flange down on top of a sheet of paper, check till you just see a wet spot which should show where the leak is. Especially if the water never shows up anywhere else. Or balance on a circle of glasses or shot glasses where each bolt drips into a different glass.

Yes, the leaking bolt has been identified using a tub/sink stopper to plug the element hole, and checking where the drops form.

Ben Z. wrote:Sucks that they are through holes. Looks like one option would be to tap for the next size up, install a stud, and then have someone run a small weld bead around the base of the new stud on the outside. The threads would take the load - the weld would just stop the leaks. Could also braze/silver solder the stud in the hole. Doesn't look like the flange would care if you opened up one of the three holes a bit to accommodate the bigger stud.

A bigger stud likely won't fit through a standard element flange hole so yes, the element would need a mod too. Tapping (especially this size) stainless steel is quite difficult and I'd still need a machine shop. I also have no experience soldering anything else than small electrical circuits. I have to ponder all of this, and the severe lack of time for this kind of tinkering, versus just entering my credit card number on the web.

I'm not minimizing the satisfaction derived from fixing everything myself, but at some point, I have to decide to move on. That saga started with a seized pump, maybe caused by a non-return valve that was stuck open, and this was just supposed to be a preventive gasket change that just ended up with me destroying my boiler... I think I just need my machine working now!

Maybe, if you want try to find a stud with double size M8 /M10 ( or the size that match the heating element flange holes) you can eventually make a bigger thread in the flange boiler.
Hoping your machine can back in business asap.

Thanks Giampiero, that's an interesting idea, although I fear I don't have the adequate equipment for rethreading that hole. Not only the tap itself is hard to find -- I'd have to get an more expensive kit -- but with stainless steel, I don't think doing this by hand is viable. I'd need a drill press I think. Also, finding those double-size studs might be difficult.

I'm interested though if you know what is the original thread/size of the threaded stud in the Pro 700 boiler. Is it M8?

Yes, the threaded stud is M8, you can even check the WLL Profitec Pro 700 Parts Diagram link, where the bolt ( part 24) is declared a M8.
https://support.wholelattelove.com/hc/e ... ts-Diagram

Now I feel dumb that I didn't check the nuts on the part diagram before.

JRising came up with an interesting idea (I hope he doesn't mind myself repeating it here). The idea would be to take a bolt (not just a stud -- something with a flanged head) and insert it in the hole from inside. An appropriate washer needs to be inserted there as well to ensure no leakage. When installing the element, the nut would tighten the whole thing, with the bolt head pressing on the washer. Perhaps I could also use two nuts, one just to keep the bolt secured and that would sit under the element flange, and the other to tighten the element.

This could work, but I'm currently trying to find a stainless steel M8 bolt with a flanged head and a washer that would resist being in boiling water for a long time without disintegrating or tainting the water.

I guess I'm not really limited to M8, perhaps 5/16 should fit nicely in the hole as well since it's not threaded. But since it would be in water for prolonged durations, I think stainless steel is a must.

For the washer, I'm trying to find more info on fiber or fibrous washers and see if it could work, but the best I guess would be some sort of silicone washer.

If I can't find a silicone washer, another possibility would be to use RTV silicone around the head and create the washer this way (it says on the tube: "gasket maker"). The disadvantage of this method is that if I need to redo this, it will be extremely difficult to remove the RTV silicone from inside the boiler for another application.

The only problem is if the internal side of the boiler flange is not regular, or if there are some welding residual around the hole.

ira wrote:If you just wrap the bolt right under the head with a think layer of teflon tape, it will crush under the bolt and likely seal just fine.

Thanks, that's a good idea. I am weary that filaments of teflon could detach an float in the boiler though. If I can find some kind of silicone washer, that would be best, but I will note down this suggestion.

Giampiero wrote:The only problem is if the internal side of the boiler flange is not regular, or if there are some welding residual around the hole.

Good point. It does seem quite flat in general but yes, there is a, uh, doughnut (for lack of a better term) of metal around the hole on the internal side. It's not sharp and it's hard to evaluate the size (I can only feel it with my finger -- less than a milimeter for sure), but it's a soft bump so perhaps it could still be sealed.