What thread sealant should I use to install a 14FHK filter housing with a sticker stating, "Polypropylene Head - Use Proper Thread Sealant”?

Any sealant that is deemed to be compatible with polypropylene is suitable. Boshart recommends the use of Gray Magic pipe joint compound which is compatible with all metals and plastics making it a great choice to have on service trucks.

Gray Magic is an excellent choice to use as a thread sealant when making connections between a water filter housing with a female NPT connection and a plastic or metal male NPT fitting. Gray Magic is Boshart's recommendation since we know this product is compatible with all types of plastics. Gray Magic is not the only suitable thread sealing paste, there likely are others on the market, however you need to make sure that the thread sealing compound you use is compatible with the polypropylene filter head material. Some sealants have been known to have adverse effects on plastics and can cause the filter head to degrade and stress crack over time.

An important thing to remember is that PTFE tape should not be used when connecting PVC/plastic fittings or valves with a female thread (FPT). If the tape is used on female connections, a wedging action can occur which will cause major stress on the joint during assembly.

NOTE: There are likely many high-quality thread sealing compounds on the market that are compatible with polypropylene, however it is the installers responsibility to verify directly with the thread sealant manufacturer that the product is indeed compatible. Many do not provide this information on their data sheets.

The following thread sealants should be compatible with polypropylene. However, this is said without 100% certainty, because manufacturers may alter their formulas without notice. Therefore, you must verify this is on their current data sheet or reach out to their technical support. These thread sealants may be an option when you do not have Blue Magic thread sealant on hand:

• LOCTITE 1537780 - No More Leaks™
• JET-LUBE V-2™ Multi-Purpose Thread Sealant
• Oatey® Great White® Pipe Joint Compound With PTFE
• Harrington Industrial Plastics LLC - BLUE SEAL PB
• RectorSeal No. 5®