Outside tap fitting

[Great_scot_selfbuild]

Basic question - should there be a rubber washer / seal on this connection on the tap to the HDPE connection (would have thought it would be supplied).

 

Thread dia is 25mm and as the photo shows, even when just nipped up, it’s off centre. 

[JohnMo]

Use a thread sealant, I like to use Loctite 55.

 

Some versions of that tap come with PTFE tape to seal the thread.

[Nickfromwales]

PTFE tape, applied so turning the tap in doesn't unravel the tape, and stop turning it into the fitting before it gets completely fully home. 21 full turns on a 3/4” thread should be Ok. 

 

The thread is 3/4” BSP, none of the threads you’ll see are metric ; 1/2” (15mm) > 3/4” (22mm) > 1” (28mm).

 

Check you're not cross-threading the tap into the plastic fitting, as it should be straight. PTFE is forgiving, so even if out a bit you should be leak free. 

[saveasteading]

11 minutes ago, Nickfromwales said:

fully home.

Is there truth, as I've had it said, that you can't turn it back again if it's not sitting quite right? 

I thought the idea was that the fibres expand when the pressure reaches them. And I have turned some back without problems.

[Nickfromwales]

9 minutes ago, saveasteading said:

Is there truth, as I've had it said, that you can't turn it back again if it's not sitting quite right? 

I thought the idea was that the fibres expand when the pressure reaches them. And I have turned some back without problems.

Yup. Even 1/4 - 1/2 a turn back off can cause it to leak. 
 

Needs taking off, cleaning, re-taping, and doing again if so. 

[Thorfun]

56 minutes ago, Nickfromwales said:

Yup. Even 1/4 - 1/2 a turn back off can cause it to leak. 
 

Needs taking off, cleaning, re-taping, and doing again if so. 

That’s why I use the loctite. Much easier for us amateurs. 

[saveasteading]

7 minutes ago, Thorfun said:

Much easier for us amateurs. 

I vaguely remember being told that 8-10 turns of tape was enough, and that it worked in the distant past. Perhaps manufacturing tolerances have changed.

Or perhaps the added bit of gunge was doing the job.

But agreed, it takes 22 and still turns on, so I do that. But a tiny turn back to square doesn't seem to have been a problem...yet.

[crispy_wafer]

I agree with the man that says loctite 55 🤣, wrap it, tighten it, back it off so it points in the right direction job's a goodun.  That said, not tried it with metal into hdpe.

[Alan Ambrose]

>>> manufacturing tolerances have changed

 

My feeling is that manufacturing tolerances are a bit variable - especially for some of the unbranded / special components. The worst I've found, so far, is some of the bits supplied for irrigation and some unusual brass threaded components I ordered from Ireland for connection to a a Stuart Turner pressurisation pump. So, '3/4" BSP' is a bit of a rough and ready thing in practice.

[Onoff]

7 hours ago, Nickfromwales said:

PTFE tape, applied so turning the tap in doesn't unravel the tape, and stop turning it into the fitting before it gets completely fully home. 21 full turns on a 3/4” thread should be Ok. 

 

The thread is 3/4” BSP, none of the threads you’ll see are metric ; 1/2” (15mm) > 3/4” (22mm) > 1” (28mm).

 

Check you're not cross-threading the tap into the plastic fitting, as it should be straight. PTFE is forgiving, so even if out a bit you should be leak free. 

 

I have followed this exact advice. Job's a good 'un.