Compression fittings to Cylinder

[TB204]

For one reason or another, I seem to have had some pretty poor quality compression fittings of late and had to rely on boss white to seal. Not sure if its poor olives (brass v copper). Anyway, I'm about to replace my indirect cylinder and while cold feed, and coil feed and return will require new connections and hence be new comp fittings, I would like to use the existing 28mm top connection (hot water feed). Can I expect problems due to tolerance differences between fittings in which case perhaps I should renew the pipe or should I rely on boss white.

Thanks for any advice.

 

[GasmanxxxR1]

Can depend on the quality of the cylinder, i like the gledhill envirofoam

 

[GasmanxxxR1]

Always put a bit of jointing compound around the pipe where the olive will sit too

 

[TB204]

Thanks Gasman.

I purchased my cylinder from Newark as I wanted specific dimensions and a grade 2 as its a hard water area and the cylinder is hard to get at.
I know that I've had problems when replacing fittings (valves etc) whereby the existing olive doesn't immediately seal. Its almost as if the depth of the hole in some fittings varies which results in the existing olive on the end of the pipe not properly sealing to the new fitting as the pipe bottoms in the fitting before the olive seals against the chamfer in the fitting (my guess as to what is happening)..... maybe its cheap fittings. However, I can generally get them to seal with some compound (although I was brought up to expect them to seal without needing it)

 

[snowhead]

whereby the existing olive doesn't immediately seal. Its almost as if the depth of the hole in some fittings varies which results in the existing olive on the end of the pipe not properly sealing to the new fitting as the pipe bottoms in the fitting before the olive seals against the chamfer in the fitting (my guess as to what is happening)

There's your problem.
Never reuse an olive, always cut or pull it off and use a new one.
And use a new nut.
With just a smear of paste on the new olive.

And yes the depth does vary.

 

[Best]

You should have been checking if the depth of fitting was less than original!
Although the compressed old olive will usually pull back towards the new fitting as you tighten the nut.
Normally better to replace the nut and olive, but if original olive looks like it hasn't been crushed much, it might be fine, particularily with quality brass olives.
Always use paste IMO, but remember ordinary Boss White paste is not for potable water.