Taper and parallel BSP fittings

[chris French]

New shower valve, cast brass body, 3/4" BSP female connections.

The instructions specify not to use taper thread fittings as it might cause damage - what damage might be cuased? cracking if over tightened?

ok, I have a couple of different types of 22x3/4" male fittings, Speedfit and solder ring, but they appear to taper thread, as do most of other fittings on websites (or they don't say).

I want to get this fitted and the studwork boarded for tiling over the weekend. I'm assuming that I can get something at my local plumbers mechants, todya/tomorrow morning but if not how much of a problem might it be using the taper thread fittings?

[John Rumm]

yes, or distortion of the valve body in some way...

The non taper ones will usually have a flange for a sealing washer to sit against.

I would go with the parallel fittings...

Is this a flush or surface mount valve?

[harryagain]

Taper threads have a powerful expanding action and always need to be tightened judiciously. If the female thread is in a soft metal or a fragile casting, it may split it/strip the thread.

Normally they can be used but only with experience. (ie knowing when to stop.)

A taper thread will normally seal to a much higher pressure and seals on the thread. Parallel threads normally have a resilient washer to make the seal.

[chris French]

Ah, makes sense,thanks

Flush

[Cursitor Doom]

Not to me it doesn't. Can't see how a taper thread can possibly work. The concept blows my brain in half. Surely both the bolt and the hole it screws into must have parallel walls of the same diameter or screwing in is simply impossible!

[chris French]

Nope.

Though the makes sense comment was in response to somethign else.