Seeping threaded fittings... *stainless/brass plastic*

[Deuce]

Pool pumps & filters are quite low pressure things even on 2" so don`t see why you struggle.
You tried these?
Mega Union coupler | Bosta UK Ltd
Come threaded for plastic or metal pipes or solvent weld

Yes we use hundreds of those a year. Fantastic as the seal is perfect each time and allows components to be switched out in moments, tool free. But sadly the pump/filter ports themselves are threaded, so threaded seal connections still exist in the system. We don't struggle so much with the pool kit really though. But when we have 3000 solenoids all with threads going into a single distribution manifold, all of which have to be (and remain) leak free, even a 99% success rate would mean 3 leaks per assembly. So that's why we're looking for quick and foolproof sealants to use.

 

[Deuce]

I can't fathom how you are having so many problems with threaded fittings.
You are obviously having major problems, hence coming on here.

Are you putting the tape on the correct way?
Is the tape not gripping to the plastic fittings and spinning / slipping.
Try roughing the threads up a little, so the PTFE grips to the thread.

We did some waterlines recently that were between 1400kPa & 1600kPa, used PTFE tape on all the threaded fittings and didn't have one drip. The largest fittings were 50mm

Not major problems, it's just the sheer number of connections and importance of zero drips that makes me seek the ultimate product/method.

But what you have said is quite concerning. PTFE is not generally good for plastic threads. It increases the internal pressure on the female fitting, which combined with a medium to long term reactions with certain plastics can cause the fitting to split. We have had that happen. As your lines were 14bar pressure any such additional pressure on the fitting could be critical.

The thing is, I agree PTFE does work very well on plastic fittings. Initially. But it's a thread lubricant, sot sealant. Any future agitation and drips tend to start. And over time as the tape shifts and compresses the same can happen. But the worse thing is, the reason it works so well on plastic is it allows you overtighten the fittings - causing a fantastic seal initially but at the expense of over-stressing the female fitting.

It does depend entirely on the type of plastic fitting of course. If it were a GF reinforced PP fitting, as many pressure fittings are, then no problem. That stuff's near indestructible. But ABS and especially PVC, teflon tape is really not correct.

We genuinely have had quite a few 1.5-2" PVC threaded fittings split due to the use of PTFE. None were above 3bar pressure. And none split due to water pressure, it was the non-design force from the PTFE that did it. Most common when we combined PTFE with silicone as this made over-tightening very easy by even the most sensitive of hands. That was in the early days and not used PTFE of plastic since.

 

[oz-plumber]

How many wraps do you do with PTFE tape on each size of fitting?

If someone asked me for a quick and fool proof method of sealing a threaded joint - I would reply PTFE tape.

For pool equipment under minimal pressure, I wouldn't consider using anything else on any size of fitting

 

[oz-plumber]

My post may seem not to answer the question - we were posting at the same time.

If you are having fitting split after a while due to stress on the fitting due to PTFE tape, I would find another type of fitting.
I would put that down to the quality of the plastic in the fitting not the jointing method

 

[Deuce]

How many wraps do you do with PTFE tape on each size of fitting?

If someone asked me for a quick and fool proof method of sealing a threaded joint - I would reply PTFE tape.

For pool equipment under minimal pressure, I wouldn't consider using anything else on any size of fitting

It really depends on the exact scenario and fittings to hand. Generally 3-4. That doesn't remove the issue of extra pressure on the female fitting though as you don't know whether or not the tape shift/creases/folds as it's tightened. 4 wraps could in one spot be the equivalent of 7 wraps.

You're outside of most manufacturers advice when it comes to the use of PTFE on plastic. Although, if you're not willing to consider anything else, I guess you have no option!

The only manufacturer I have spoken to that does say teflon tape is ok is spears. But even they stipulate no more than two tooled turns of the threads beyond finger tight. Effectively leaving at least half the thread exposed in most cases. And in any case, they like others prefer the use of sealant in general.

It also has little to do with line pressure. Yes swimming pool kit is relatively low pressure. But I have seen pvc fittings split due to PTFE use on drained systems sat in storage.

 

[Deuce]

My post may seem not to answer the question - we were posting at the same time.

If you are having fitting split after a while due to stress on the fitting due to PTFE tape, I would find another type of fitting.
I would put that down to the quality of the plastic in the fitting not the jointing method

We do keep crossing posts but all useful stuff!

Yes I agree. and per my last post, this may well be why Spears are OK with PTFE tape. The quality and conformity of their fittings is above average imo. Perhaps the worse fittings we have come across are the 'mega' fittings range. We once had a union roll off onto the workshop floor and split. We ripped it apart for a closer look and there were voids in the PVC wall!! I would think that more premium fittings are weighed during production for conformity.


But still the fact remains - PTFE can apply spot pressure to the female fitting which increases failure potential. And it will often drip if agitated after an initially successful seal. It's a common enough problem and if you google it, it's not hard to find examples and various experts explaining at length the reasons why it's not ideal.

 

[Deuce]

So.. the 5776 arrived this morning. I grabbed a couple of old 1.5" fittings, one brass, one stainless and applied to product to the male thread, and finger tightened. I left it about an hour and noticed the product was still fully liquid, I had expected it to gel over at least. But anyway, it said it would work after a few minutes so I hooked it up to a pressure tank we have and then wound the pressure up to 3 bar. That was 2 hours ago and no drips. Not bad for old fittings, finger tight and no real care in the application of the product.

So I'm very happy so far! It still hasn't 'cured' in any way. I'm not sure if it will - but clearly whatever it's doing inside the threads in working. It's also locked the two fittings together very well. I'm sure I could break them apart if I tried but already better than PTFE when it comes to resisting movement.

When i've broken the fittings apart I'll repeat the test, this time applying pressure after just a few minutes. I have a feeling it'll still work fine.

I haven't had chance to try the plastic thread sealant yet, but I'm optimistic based on how well the metal thread sealant works.

So thankyou to all who contributed to this thread - I'm very grateful!

 

[ShaunCorbs]

It won't cure for a long time you can wipe it away once you've finished tightening to make it look neat

 

[Deuce]

It won't cure for a long time you can wipe it away once you've finished tightening to make it look neat

Good to know. And yes it's certainly neater than general sealants we have bought over the counter in the past. This is far better. Even at the price, which is irrelevant really if it works this reliably.

 

[Chuck]

5776 is an 'anaerobic cure' adhesive. For it to cure it requires (a) absence of air (oxygen in fact) and (b) the presence of metal. See here for details:

Thread Sealant | Thread Sealing | LOCTITE® - Henkel Adhesives North America

So, the reason your excess doesn't cure is that it is in contact with air. Clever stuff.