Are these garden tap threads compatible?

[raymondo]

J

ust a quick question. I am aware that mixing Brass and steel, is potentially chemically unstable. But are the threads meant to be compatible, at least?   They are both half inch, BSP. .

I find that three or four turns is all that is possible, if that. 

(Brass half inch garden tap and half inch Galvanized steel coupling.)

Thanks...

[BoeingFan]

Wow, I never knew that mixing brass and steel was potentially chemically unstable. I bought some brass hose fittings for a dishwasher the other day, and one of the fittings was out of stock in brass, so I just bought the silver one (I assume it's steel). I look forward to the Bunnings team (perhaps @EricL?) replying to shed some light on this.

[Jewelleryrescue]

Hi @raymondo 

Yes  dissimilar metals can setup galvanic corrosion between them and speed up the metals natural corrosion but this process would take years  as the metals are not to far apart on the periodic table.  certainly time to get to bunnings and new parts. 

The other factor is the relative hardnesses of the two metals in the case threads arnt exactly the same one can damage the other. Alot of this i mitigated by the  use of plumbers teflon tape which acts like a lubricant and sealer at he same time. The Brass tape wont screw fully into elbow as the elbow is too shallow  fr the  tape thread so the only way to seal  this union is plumbers tape.

Remember to wind the tape onto the tape thread anti clockwise approx 6 turns  while looking at the front of the tape to stop it unraveling during tightening.

[Noyade]

Yes, they are compatible @raymondo, like all the other hundreds of thousands of outdoor taps in Australia set up the same way.  😁

I have three.

After your "four turns" was it watertight? Did you try it?

[EricL]

Hello @raymondo

It's great that you've received fantastic advice from @Noyade and @Jewelleryrescue. Just to add my vote, yes the garden tap is compatible with the galvanized elbow threads. If you want a leak-free installation use thread tape along with  BOSTON 50g Liquid Sealant. Apply the sealant liberally on the threads before screwing it into the elbow.

If you need further assistance, please let us know.

Eric

[raymondo]

Thanks Eric.

I find it hard to believe what everybody is saying. I guess it depends how we define "compatible".  I bought a bunch of  fittings from Bunnings the other day, and none of them will go more than a couple of turns, except brass to brass. The galvanised steel fittings appear to be the real culprit. They don't even but up nicely to their own kind. ( as in the picture below.. 2 1/2 turns by hand)

I realize they are one third the price of brass, but does that mean they have to be shoddy?  I am also aware they have been around  for decades. Maybe we've just got used to poor quality. 

I live in a rural Sale, where my farming neighbours definitely don't consider the brass and steel compatible. 

Although they are both half inch, and both BSP, doesn't mean the quality is the same. 

True... taping them does produce an adequate seal, but it can still be hit and miss. 

That's life isn't it... 

Cheers

[raymondo]

Thanks for that..

[raymondo]

Thanks for that..

The taping helps. You might like to peek at my response to Eric.

Cheers

[MitchellMc]

Hi @raymondo,

Galvanised fittings have a tapered thread cut into them. They are designed to go on easily, and then the more turns you do, the tighter they get. They are not necessarily designed for the entire cut thread to screw into the fitting; an exposed section can remain. I note that you mention above that you get about two and a half turns by hand. I just ran out to a store and tried the fittings myself to see if something was amiss. I'm able to easily screw almost the entire thread in by hand, with both the brass tap into a gal fitting and gal-to-gal fittings. In some cases, this is up to seven rotations. The male thread actually engages to the full depth of the cut female thread and only stops when there is no more internal thread for it to engage with.

For instance, for the last tee fitting you've pictured with the nipple, I can screw that nipple into the tee entirely in by hand, so there is no thread exposed. So, perhaps the fittings in your location are from a different supplier. You might find that the galvanised coating could be preventing the thread from screwing on easily. How many rotations do you get with a pipe wrench?

If you can let me know the store you purchased the fittings from, I can certainly provide your feedback to the supplier and determine whether this is an issue with the products.

Mitchell

[Noyade]

A warm Sunday morning experiment.

Regards the thread tapering.

Tap and gal fittings below are from Bunnings.

There is no way, by hand, I can insert the tap any further. Tapering binds the tap for a better watertight fit.

Hand tight insertion.

I definitely know the P&N pipe die produces a tapered thread that binds after a short distance - you simply cannot cut any further.

The outdoor taps I have - none are able to utilse the full tap thread into the gal elbow even with a pipe wrench and shifter.

Good thing methinks.

Hi @MitchellMc 

"I just ran out to a store and tried the fittings myself to see if something was amiss."

I have read one sabotage technique used in Nazi slave-labour factories was to machine nuts and bolts at the extreme opposite ends of their tolerances such that the nut would bind quickly on the bolt - and become ineffective.

I wonder. 😁