# Sealing Threads



## dan1502 (Sep 8, 2012)

I'd appreciate a bit of advice.

I've had issues with the anti-vacuum valve on my Expobar twin boiler machine (pre-PID model not that it matters).

I've ended up replacing the valve though I could probably have got away with replacing the O-ring.

I used PTFE when replacing the valve and had trouble with leaks and actually ended up refitting the old valve with PTFE and all was fine for a while but as it leaked again I've now put the new valve on.

Anyway I fitted the new valve today and tried it with no PTFE and it seems fine. There was still a slight hiss which I have now found to be the safety valve. So I removed the safety valve and tried to clean it but it won't come apart properly. I refitted it without PTFE and it had to be very tight to stop hissing.

I've now ordered a new valve.

So, onto my question. Should I use PTFE? There didn't seem to be any when I removed the valves but there was perhaps something. Is there a food safe thread sealant I should/could use (type of Loctite)? Or should I use nothing.

I've seen threads on this before but nothing that has made me certain.

Thanks


----------



## funinacup (Aug 30, 2010)

I usually refit anti vacs and safety's with PTFE as standard (on advice of engineers). Never usually experience leaks and that's just with one turn of tape.


----------



## DavecUK (Aug 6, 2013)

I always use PTFE


----------



## dan1502 (Sep 8, 2012)

Thanks. I have always used PTFE before but just tried the new anti-vac today without. This is fairly loose fitting but seems to seal when tightened down despite there being no washer. Perhaps using too much PTFE previously caused it not to seal properly.

The safety valve is a very tight fit. I'll probably try one turn of PTFE as suggested but was also considering trying food safe high temperature loctite, left to cure for 24 hours.


----------



## El carajillo (Mar 16, 2013)

You should be fine using PTFE, the usual cause of leaks with PTFE is not putting sufficient turns on, OR winding it the wrong way /not tightly enough. Depending on fit of threads, for small /fine threads 3 / 4 turns should be sufficient. It should be wound on the opposite way from which you will rotate the thread. Ie for a normal thread R/H, with the thread pointing upwards wind the tape clockwise.

If you use Loctite make sure you obtain the correct one, suitable for contact with drinking water /food also that it is for demountable fittings. ie that you can take it apart if you need to.


----------



## dan1502 (Sep 8, 2012)

Thanks. I'm ok with turning it the correct way. Sometimes the issue can be getting enough on (and tight enough) when the length of the threaded area is short which is the case with the new anti-vac valve. Also I have two thicknesses of PTFE, one being a lot thicker than the other. Sometimes if the thread is very tight it can just be pushed up out of the way too.

I was thinking of Loctite 567.


----------



## El carajillo (Mar 16, 2013)

The thicker PTFE is usually for gas pipe work, is it a yellowish colour ?


----------



## dan1502 (Sep 8, 2012)

It's white but on a yellow spool so probably is gas specification. I think I'll try sealing both valves with 3 or 4 turns of standard PTFE and if that doesn't work I'll try the Loctite 567 which I've ordered just in case as it will be handy to have around for other jobs anyway.


----------



## dan1502 (Sep 8, 2012)

I've just been reading a bit on the US forums about the Expobar Brewtus and it seems that Expobar tend to use thread sealants at the factory (perhaps even in places where they shouldn't) which would explain the residue evident when removing components. At least it's holding pressure well enough for me to make a coffee whilst waiting or the new safety valve


----------



## JohnPrime (Nov 2, 2014)

Liquid PTFE may be an alternative. Haven't checked the data sheet ...


----------



## DannyMontez (May 19, 2014)

You could try some loctite tape. One wrap and you're golden.


----------



## dan1502 (Sep 8, 2012)

I got a decent valve the same make as the original for £12 vs more than double expobar valves were advertised at and the Loctite 567 finally arrived yesterday. It's worked very well. The datasheet says it cures completely in 72 hours but faster if hotter so I left it about 16 hours before switching on. It's supposed to be effective straight away to an extent but I thought it best to give it a bit of time. I then left it on to heat up for a while before passing any water through then flushed the boiler using the hot water tap and ran steam for a while. It smells pretty bad when curing. It's hard to judge whether there's much of a taste as I am just trying a new blend! I was careful to apply it such that there shouldn't be much if any exposed though.


----------



## dan1502 (Sep 8, 2012)

Just to conclude after a week of use that I found this very easy to use and to do an excellent job.


----------



## espressotechno (Apr 11, 2011)

Blimey - what a palaver !

PTFE tape, or occasionally a thick teflon washer, always works for me. Even tightening up hand-tight gives me a good seal on the a/v & safety valves.

Could be that the Expobar hole threads are slightly oversozed........

PS It's not worthwhile trying to overhaul a safety valve - the original pressure setting is almost impossible to find.


----------



## espressotechno (Apr 11, 2011)

Blimey - what a palaver !

PTFE tape, or occasionally a thick teflon washer, always works for me. Even tightening up hand-tight can give me a good seal on both valves (when testing stuff).

Could be that the Expobar hole threads are slightly oversized........

PS It's not worthwhile trying to overhaul a safety valve - the original pressure setting is almost impossible to find.


----------



## dan1502 (Sep 8, 2012)

The vacuum valve sealed ok without anything though it did have to be nipped up quite tightly. I didn't try the safety valve without anything. The information about not having to tighten it much would have been helpful to know before I did it.

I was led to believe that PTFE or a threadsealer was a good idea anyway as it prevents seizing due to corrosion or oxidisation. A teflon washer would probably have worked fine but I didn't have any of the correct size. The sealant was very easy to use and I believe it can easily withstand enough pressure for this application without curing but it was no problem for me to leave it over night. I've had no nasty taste either.


----------



## DavecUK (Aug 6, 2013)

If the threads have had thread locker on them before and are not well cleaned, sometimes they can be difficult to seal, but I have never had a problem with PTFE, 4 to 7 turns for cozarse threads, don't use gas tape and it's good. I hate thread locker and try to persuade manufacturers not to use it. Anyone who has had to repair machines a little will usually have a hatred of thread locker.

PTFE Tape also makes the fittings very easy to get off in many years time!


----------

