Recommend a Jointing Compound (for Compression Fittings)

paperclap

Hi all,

I'll soon be replacing all our old radiators with new radiators, along with new TRVs.

I know some people use jointing compound on their compression fittings, whereas others don't bother at all. However, for the sake of £5 a tub or tube (of whatever I choose to get), it sounds like a good insurance policy to me.

What is best to use?

Fernox LS-X
https://www.screwfix.com/p/fernox-ls-x-leak-sealer-50ml/23614

Fernox Hawk White
https://www.screwfix.com/p/fernox-hawk-white-jointing-compound-400g/69694

Fernox Water Hawk
https://www.screwfix.com/p/fernox-jointing-compound-400g/21548

From my understanding, LS-X is for external use (when the joint is not being taken apart, for example). Hawk White is used for non-potable water areas (such as central heating). Water Hawk is used for potable water areas. Are these assumptions correct?

This begs the question: Why would anyone use Hawk White over Water Hawk? Is the application different? If not, why not save yourself the hassle and simply have one tin of Water Hawk in your toolbox?

Thanks in advance.

FreeBear

You do not need jointing compound on compression fittings. The olive is the part that provides the seal. PTFE tape should be used on taper thread fittings (the tails that screw in to the radiator).

Grenage

You don't need jointing compound, as Freebear says.  That said, I do put a little smear over the top of the olive.

I use potable compound regardless.

Another_Level

Yes use a product like lsx (although over priced)  or purchase screwfix own brand flowmasta external leak sealer. some say its the same stuff.

Just finger apply a small amount on the copper pipe in between the olive and the valve/compression fitting sealing
area, apply a small smear on the first 3 male threads. 

Remove any excess immediately after the joint is made 

Back in the day when compression fittings and copper pipe were made in the UK, there was no need for any sealant. Now compression fitting components are made in china and copper pipe in various countries = Quality is pants 

For your job the copper pipe will be old (which is good) and the fitting components will be new imported. Apart from assistance to create a gasket type of seal on the old pipe smearing a little on the male threads reduces thread tightening friction.

Others will always disagree but i am old, seen it all before 

Anyone buying copper tube, buy british keep these guy's in work  https://www.youtube.com/watch?v=efJlWIqbC88

Bendy_House

Everything that Another_Level says, in my opinion.

I always use a smear of Fernox Hawk White on compression fittings, and in the two places A_L suggests - over the olive (I'll usually give a tiny smear on the pipe, too, (although not really needed, this will take care of any surface scratches that could be on the pipe) and then slip the olive back over this, wiping the rest over the olive), and then on the male thread.

I've had fittings before that screeeeched when tightened due to lack of lube, and possibly being poor quality. Hawk on the threads provides lubrication, so the main tightening effort you'll be experiencing is the actual compressing of the olive, so it gives a better guide 'feel' too of how much the fitting itself needs to be 'good'.

It might not be 'needed', but imo it makes the fittings much better to use, and adds a further level of security. And there are no drawbacks that I am aware of.

paperclap

Thanks all.

Yes, I had planned to use PTFE tape on the threaded joints.

That was my thought process, too. It's not needed, but just acts as a second layer of protection.

However, why would one chose Hawk White over Water Hawk?

NSG666

PTFE on the tails going into the radiators.
Many say nothing on the olives but many others use something.
I found LSX a bit messy and a short shelf life but probably not an issue for you.
For many years I used Fernox Water Hawk Jointing Compound 200g (toolstation.com) as it does drinking water too.
Then I picked up some of this to try and not been disappointed Tru Blu Pipe Thread Sealant 50g (toolstation.com)

paperclap

NSG666 said:

PTFE on the tails going into the radiators.
Many say nothing on the olives but many others use something.
I found LSX a bit messy and a short shelf life but probably not an issue for you.
For many years I used Fernox Water Hawk Jointing Compound 200g (toolstation.com) as it does drinking water too.
Then I picked up some of this to try and not been disappointed Tru Blu Pipe Thread Sealant 50g (toolstation.com)

Thanks NSG666.

Water Hawk seems like a good universal solution.

But why is Hawk White even a product, if Water Hawk does everything Hawk White does and more?

NSG666

laurencewhymark said:

NSG666 said:

PTFE on the tails going into the radiators.
Many say nothing on the olives but many others use something.
I found LSX a bit messy and a short shelf life but probably not an issue for you.
For many years I used Fernox Water Hawk Jointing Compound 200g (toolstation.com) as it does drinking water too.
Then I picked up some of this to try and not been disappointed Tru Blu Pipe Thread Sealant 50g (toolstation.com)

Thanks NSG666.

Water Hawk seems like a good universal solution.

But why is Hawk White even a product, if Water Hawk does everything Hawk White does and more?

Cheaper for those who don't work on potable water systems.

fezster

Whilst jointing compound is not always necessary, it doesn't hurt and will ensure a water tight seal every time with compression fittings without having to go back and redo them if a small weep does occur.

IME, hawk white is easier to apply than water hawk, which is why most plumbers I've come across prefer to use it for non-potable water applications.

paperclap

That's really the only difference? The price difference is pennies!