Compression fittings with hard tube

[Habs24]

This is probably a stupid question but I'm new to water cooling so I want to make sure before I waste my time and money.

I'm starting to look at compression fittings and have a question about metric to imperial sizes.

Is it safe to interchange 16mm and 5/8" compression fittings on a 16mm OD tube? Or the reverse a 5/8" tube with a 16mm fitting.
I see lots of places that list these fitting sizes as equal but 16mm is slightly bigger than 5/8".

Can the fitting compensate for the small difference or is it not worth the risk and I should just stick to all the same sizing.
I haven't bought anything yet so I can easily stick to one size for tube and fitting, I'm just always finding fittings in/out of stock in the wrong size.

Thanks for the advice

[Hooded]

The difference between 16mm and 5/8" is only .004" or .125mm. For hard tubes the O-ring is enough to cover it. For soft tube you will need to be more careful. 3/8" is .475mm or .018" smaller than 10mm. So using standard tube with metric fitting could be very tight. The inside diameter will cause the OD to grow too much to work. Using Metric tube with standard fittings will be loose on the barb and very tight on OD.
Best is not to mix the two.
1/2 and 12 mm simply won't work and can not be messed with.
And to the forum

[Akira749]

The vast majority of the brands uses metric measurement and the most popular one using imperial measure is Primochill. So I assume you're probably talking about Primochill products for the imperial brand vs any other brand.

In the soft tubing universe, the difference is not that significant and you can usually use a metric fitting with imperial tubing without issues.

But in the hard tubing universe it's not the same since you don't put your tubing on a barb and then secure the tubing with the compression ring. You usually insert the tubing inside the fitting (with an o-ring down there to make a snug fit) then you add a secondary o-ring on top of the fitting and you secure the assembly with the compression ring.

Since you simply insert your tubing into the compression fitting, the inside diameter on the fitting needs to be extremely close tp the outside diameter of the tubing. So if you put a metric hard tube into an imperial fitting it might even not insert and using an imperial hard tube with a metric fitting would be playing with the risk of an unnecessary leak.

So long story short, stick with imperial or metric but don't mix them when you go with hard tubing.

[Akira749]

Hooded ninja'd me because I took to long to write lolll.

[Hooded]

Lol

[Habs24]

Hooded ninja'd me because I took to long to write lolll.

Haha

Thanks for the help guys, think i will just keep it simple and stick to one size