British TRV in an NPT Cast Iron Rad

Champlain

Hello,



I was given seven 26" 4 column cast iron rads which I'd like to use to replace the fin&tube rads, recently leaking, in my home. The problem is, the very old rads are BSPT with new Myson BSP 1/2" Thermostatic radiator valves (TRV), which I'd like to use as well. Is there an easy way to put these two together? I understand the differences between the 1/2" BSP and NPT in terms of angle, shape and thread count. Some of the suggestions I've been given are:

1. "Just wrap allot of teflon tape around the male BSPT fitting and force it into the 1/2" NPT bushing." Even at 14 Thread per inch each side (BSPT and NPT) I figure that this might eventually leak.

2. Replace the 1/2" BSP nipple (male) part of the union fitting from the TRV with an NPT nipple from and NPT union. I don't know if the mating union flanges are the same dimension and shape for BSP and NPT. Would the BSP flange seal with the NPT flange.

3. Buy new TRVs. I've found them for about $100 each locally (sensor and body), which is allot of $$

4. Tap my own 1/2" BSPT bushing (female inner thread) and replace the radiator bushings. I've found a source for the 1/2" BSPT tap.



Thanks for your help.