Using existing olive on pipe

[diyjunky]

Thank you all for making very helpful suggestions.

My primary concern is the bottom tee underneath the magnetic scale inhibitor. Not only is it very short and hard to cut cleanly if necessary, I have no idea of the physical strength of a such a joint. If it leaked, I would be in a very difficult position particularly as the stop cock doesn't seal properly.
I suppose I could turn the water mains off in the street but I am not sure if that's legal ?)
I bought an olive puller (at a stupid price) and practiced on an old pipe. It was a brutal ordeal that left the pipe end scratched and useless.

 

[Madrab]

A properly soldered joint can be considered part of the pipe, i.e it should be as strong as the rest of it.

Yes, it's legal to use the toby in the street but you should have a means of mains isolation in the house.

Re the old olive - to give you an idea - a compression nut shouldn't be on much tighter than finger tight then say a full turn to seal properly, therefore the olive should be able to be removed using a pair of grips or pliers, I remove them using vice grips just tight enough to grip, if it won't go with them then they're cut off.

Any tighter then the olive is starting to be over-compressed and deformed. Chances are the one you 'pulled' was on so tight, that's why it wrecked the pipe coming off. That can be why a junior (edit) hacksaw just through the olive enough, then a plain screwdriver into the cut to snap the olive can work best, very similar to olive cutters but they are silly priced too, then you can see if the pipe has been deformed too.

 

[johnny2007]

Also, crucial question: is it a copper or brass olive?
I find brass olives at lot better at sealing copper pipes and much more resistant to deformation.
They can be nipped a lot tighter than copper olives without losing shape and in my experience can be re-tightened making a perfect seal.
But they're more difficult to remove.

 

[diyjunky]

We shall be doing the work tomorrow, guess I'll find out then. In my personal experience, it seems unpredictable as to whether you get brass or copper olives with compression fittings. I'd read that copper is preferable when using PEX pipe - I suppose that make sense as copper is softer than brass. To be honest, I hadn't really considered the various virtues of the two materials. The only thing I'd noticed is that brass olives sometimes have grooves cut in them. Maybe this helps the harder alloy squash more easily. Also, I would have assumed that brass is more expensive than copper yet even the cheapest of fittings can come with copper olives.

 

[Madrab]

Nope, other way around, copper is more expensive than brass, hence why a lot of suppliers now have brass instead of copper in their fittings. I always use copper olives, I buy them in bags of 100. I find them much more reliable than brass, that and I find they are the best for any plastic with compression.

With copper olives it's hand tight and no more than a full turn usually, with brass it really needs to get to the squeak point as that's when it's starting to compress the lip of the olive.

 

[johnny2007]

with brass it really needs to get to the squeak point as that's when it's starting to compress the lip of the olive.

That's why I like them, it gives a better sense of grip.
Of course with plastic pipes it's copper olives every time.

 

[diyjunky]

Denouement ...
The non return valve and the mini expansion vessel ahead of it did the job ie the combi no longer fires up (the fan at least) when the cold water taps are turned off. Fitting the non return valve is a faff but usually necessary if you have a water meter.

The configuration we ended up with was such that the non return valve (the spring type) is fitted flowing upside down. It loops back to the boiler in the correct flow direction. Seems to work fine, hope this is OK.

The End.