I plan to install a rather small site glass for a Regner Max.I was advised to not use O rings but use PTFE Tape. Can someone explain,Or a direction towards a detailed video How to install.Thank you.
First time at Installing a site Glass.Info needed please.
- Thread starter Rob1962
- Start date
I would suggest you can use either. Certainly on the bigger ones I use 'O' rings, If you want to try PTFE then take a short length and twist it into a string before you wrap it round the glass (don't forget to put the nuts on first). Either way don't overtighten the nuts. You only want to stop the water from going OUTSIDE the tube! 
PTFE tape would be my prefered method of sealing the sight glass fittings into the boiler threaded bushes. However I would avoid using it to seal the sight glass itself into the fittings for the following reasons ....
- O rings provide the most reliable seal for the minimum initial compression - assuming of course you're using the correct design of fittings with the right size O rings.
- O rings require relatively little skill to install - compared to that reqired to twist a 'string' of PTFE and then cut it to the correct length - especially in smaller sizes.
- Even if you have the requisite skill, PTFE tape will require a higher initial compression to seal both the join and the helical creases inherent with the twisting process. This may not be a problem in all metal applications but, where glass is involved, minimising the stresses is always a good thing.
- Another reason that the required sealing pressure between the O ring and the glass is less than with tape is, because it is partially derived from the pressure in the boiler and is consequently proportional to that pressure.
- O rings are better able to cope with any miss- alignment between the glass and the fittings.
- O rings provide the most reliable seal for the minimum initial compression - assuming of course you're using the correct design of fittings with the right size O rings.
- O rings require relatively little skill to install - compared to that reqired to twist a 'string' of PTFE and then cut it to the correct length - especially in smaller sizes.
- Even if you have the requisite skill, PTFE tape will require a higher initial compression to seal both the join and the helical creases inherent with the twisting process. This may not be a problem in all metal applications but, where glass is involved, minimising the stresses is always a good thing.
- Another reason that the required sealing pressure between the O ring and the glass is less than with tape is, because it is partially derived from the pressure in the boiler and is consequently proportional to that pressure.
- O rings are better able to cope with any miss- alignment between the glass and the fittings.