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Suggestions on how I should correctly seal this value

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Discuss Suggestions on how I should correctly seal this value in the Plumbing Jobs | The Job-board area at Plumbers Forums

Crooksy88

Crooksy88

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What should be a straight forward connection is proving to be something annoyingly different.

I have a 1/2 inch compression coupler which I am attaching to a new shower mixer valve (cold inlet).

The photo doesn't show this but I have applied what I thought was adequate PTFE tape (10 rotations) and before screwing the coupler in I inserted a 1/2 inch fibre washer into the valve.

Having tightened the coupler as much as possible there is a very small leak. I'm assuming the olive joint is OK but to be honest I'm unsure how to tell which joint the leak is coming from.

I'm wondering if I should be screwing the coupler in until it sits on the brass shower valve (i.e. it can't tighten any further).

Would anyone have any suggestions as to what I might be doing wrong or solutions for me to try (other than getting a plumber in :D).

Thanks,

Mark

IMG_0250.jpg
 
Use loctite or more wraps of PTFE. Plumbing isn’t about tightening everything up until it’s straining at the seams. It’s about having the experience to know when something is tight enough from feel
 
Loctite 577
 
The coupling is touching the backplate, more ptfe required to seal the joint before this can happen.
 
I like to use gas PTFE tape- yellow rolls. It's thicker than standard PTFE tape.

Seems to seal better for me on things like radiator tails.

Make the tape 'cone' shaped so the first thread has little or no tape and it gets progressively tighter as you screw the fitting in.
 
Thanks for all the advice.

It does make sense that when using PTFE if I can tighten the coupler down to the valve without much resistance then I need to use more PTFE.

Looking into sealants like Tru Blu, Loctite 577 or 55 and considering these pipes are being boxed in I think I'm going to go for 577 to give my novice pipework the best chance of remaining leak free.
 
It's a common problem with people DIY plumbing with PTFE. It seems like you are putting too much on when in reality it's actually not enough. I would start with around 15 or 16 wraps of PTFE tape and see how it tightens in. If I'm not happy with the feel of it as it tightens in I'll try it with another 4 - 5 wraps. Usually good by that point.
 
Before applying PTFE to threaded joints I connect the joint counting how many revolutions until it comes to the end. Helpful if aligning taps, etc.
Apply PTFE and if there is enough on, the joint will lock up before maximum revolutions reached. On deep-cut threads, it may be be wise to try on fitting part way to seat tape into threads, then undue for a further wrap or two.
As previously said, experience can tell you when its right.
Valid point made about having pipe straight into olived joint. Finger tight first, to check if straight, and then apply elbow grease via spanner.
 
Andy B said:
I like to use gas PTFE tape- yellow rolls. It's thicker than standard PTFE tape.

Seems to seal better for me on things like radiator tails.

Make the tape 'cone' shaped so the first thread has little or no tape and it gets progressively tighter as you screw the fitting in.
Click to expand...

Sorry Andy.
Great minds think alike.

I obviously didn’t read the last sentence of your above post and posted the identical thing.
Only you worded it better with the “cone” description. :)
 
Before you put any tape or string on the fitting roughen the thread with a file or hacksaw blade. The tape will then stay put when you wind the fitting in.
I do this on ALL threaded seals, it makes a big difference. Loctite 55 for me.
 
You'll find most pipe fitting thread forms come in both parallel and tapered variants.

With a tapered thread form it is the thread itself which forms the seal as the male and female sections tighten together. To prevent spiral leaks a small amount of thread tape is used to fill the small gaps.

On the other hand parallel thread forms are designed to seal either with a the addition of a washer or some form of sealing compound which cures anaerobically.

As far as I'm aware domestic plumbing fitting used in the UK are BSP parallel so you're always going to have problems sealing with PTFE etc.

You may get away with it on very low pressure applications such as radiators but even then weeps and seeps are quite common with time.
 
OffshoreGas said:
As far as I'm aware domestic plumbing fitting used in the UK are BSP parallel so you're always going to have problems sealing with PTFE etc.

You may get away with it on very low pressure applications such as radiators but even then weeps and seeps are quite common with time.
Click to expand...

Usually only weep through time if joints were done wrong though, - often due to not enough ptfe tape.
 
OffshoreGas said:
Parallel threads aren't designed to seal with tread tape. You need a gasket of anaerobic thread sealant of some sort. If you ever have the misfortune to do a pipe fitting course they will bore you to death with this. Have a look at the literature on pipe or tube fittings, chucking a ton of PTFE tape on is not the correct way to seal a parallel thread.

Parallel Threads vs Tapered Threads | Swagelok
Click to expand...


On parallel threads we can still easily seal them with ptfe tape.
I see no reason to use anything else on rad tails or most other male threads.
Rads, oil boilers, copper and stainless steel cylinders, some shower valves, all are parallel threads and normally perfect seal.
 
Best said:
On parallel threads we can still easily seal them with ptfe tape.
I see no reason to use anything else on rad tails or most other male threads.
Rads, oil boilers, copper and stainless steel cylinders, some shower valves, all are parallel threads and normally perfect seal.
Click to expand...

Agreed, as I said you may get away with it, may leak when you fit it, it may leak in 6 months time. Why not use the right product/method from the get go?
 
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