Jun 04, 2020 - 05:42 AM
Whenever possible we recommend using a straight thread with an O-ring (Viton/FMK) for all fittings they are much easier to use and far more reliable than tapered pipe threads (like NPT or BPT).
However when you are using standard sized pipes NPT and BPT (DIN) are the only thread types available. This is one reason we always recommend cPVC pipe and fittings as they are welded together using primer and glue and they almost never leak after they have been properly attached and allowed to cure (we alway give it at least 1-2 hours to really cure).
Regardless NPT and BPT fittings can be notoriously difficult to seal as they rely on the compression of the actual threads on the pipe.
When sealing threads here in the Engineered Fluids lab we always use the following:
- PTFE thread tape: This works 90% of the time and we find no difference in reliability between white or yellow tape.
- We like this product its easy to use: https://www.fluoramics.com/store/formula-8-3-5-oz.html?category_id=24
- This product works as well in place of #1: https://www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_5113.htm
- On fine threads we use: https://www.henkel-adhesives.com/us/en/product/thread-sealants/loctite_545.html