RV PEX Plumbing Fittings Guide: Crimp vs SharkBite vs FIP Connections Explained

The Quick Answer

For your RV water manifold and pump connections, you want 1/2" FPT (Female Pipe Thread) fittings, not compression fittings. RV water systems typically use NPT (National Pipe Thread) connections, which means your manifold and pump likely have 1/2" MPT (Male Pipe Thread) connections that require FPT fittings to mate properly. That braided faucet supply line you linked from Home Depot with 1/2" FPT connections is exactly what you need for the manifold-to-strainer line. Compression fittings won't work properly on NPT threads - they're designed for different applications and won't create a reliable seal on your RV's threaded connections.

What's Causing This

You're absolutely right to be frustrated with RV manufacturers' plumbing choices. The mix of PEX compression rings on reinforced flexible hoses is a cost-cutting measure that creates potential failure points. PEX compression rings are designed specifically for solid PEX tubing, not the reinforced flexible hoses commonly used in RVs. The reinforced hose has a different outer diameter and surface texture than PEX, which means the compression ring doesn't create the same reliable seal.

The reason manufacturers do this is simple economics - they can use the same PEX fittings throughout the build process rather than stocking different types of connectors. However, this creates exactly the situation you're describing: connections that work initially but are prone to failure over time due to vibration, temperature changes, and the natural movement of an RV. Your proactive approach to replace these before they fail is smart, especially with the manifold and pump located under the bed where leaks could cause significant damage before being discovered.

The threaded connections in RV water systems are indeed NPT standard. This includes your water manifold, pump connections, and most other plumbing fixtures. NPT threads are tapered and designed to create a seal when threaded together, often with pipe thread sealant or tape. Compression fittings, on the other hand, rely on a ferrule or compression ring to create the seal and are typically used with copper tubing or specific compression-compatible materials.

Tools You'll Need

• Adjustable wrenches (two - one to hold, one to turn)
• Pipe thread sealant or Teflon tape
• Bucket or towels for water spillage
• Flashlight or work light for under-bed access
• Needle-nose pliers for tight spaces
• PEX compression sleeve removal tool (if you're replacing PEX connections) - use to slide back compression sleeves and remove old PEX fittings
• Larger compression clamps you mentioned for reinforced tubing
• Barbed fittings to replace PEX fittings on manifold

Step-by-Step Fix

SAFETY WARNING: Before beginning any water system work, turn off electrical power to the water pump using the pump switch and/or pull the pump fuse. Drain the system completely and ensure no pressure remains. Water and electricity can create dangerous conditions.

1. Turn off water pump and disconnect the city water inlet hose. Open a faucet to relieve system pressure and drain the lines as much as possible. Verify system is fully depressurized before proceeding.
2. Access the area under your bed and identify all connection points on the water manifold and pump. Take photos before disconnecting anything to reference the original configuration.
3. For the manifold-to-strainer line replacement: Remove the existing flexible hose from both ends. The manifold side likely has a 1/2" MPT connection, and the pump strainer should also be 1/2" MPT.
4. Install your new braided supply line with 1/2" FPT connections. Apply a thin layer of pipe thread sealant or 2-3 wraps of Teflon tape to the male threads before connecting. Tighten to manufacturer specifications - typically hand tight plus additional turns until tapered threads properly seat (see manufacturer specs for specific torque requirements).
5. For the manifold barbed fitting conversion: Remove the existing PEX fittings from your manifold. You'll need the correct MPT to barb adapters for your model (verify with dealer) - these are available from RV supply stores or online. Brass versions are available from places like Camping World or RV Parts Country, though you may need to search for "brass MPT to barb adapter" rather than "swivel barb fitting."
6. Install the new barbed fittings with thread sealant, then connect your reinforced hoses using the larger compression clamps you found. Make sure the clamps are positioned over the barbed section for maximum grip.
7. For the city water inlet PEX connection: Install your PEX-to-barb converter and connect with reinforced hose and proper compression clamp.
8. Turn water back on slowly and check all connections for leaks. Run water through the system and inspect under pressure.

When to Call a Pro

This is definitely a DIY-friendly project for most RV owners, but consider calling a professional if you discover your water manifold has unusual thread sizes or configurations that don't match standard NPT fittings. Some European RVs or specialty units might use metric threads or proprietary connections that require specific adapters.

Also call a pro if you find evidence of existing water damage when you access the under-bed area, as this might indicate other plumbing issues that need professional assessment. If you're uncomfortable working in tight spaces or don't have experience with pipe thread connections, a mobile RV technician can complete this work in about 2-3 hours for $200-400 depending on your location and the extent of the modifications needed.

Regarding those brass swivel barb fittings you're looking for - try searching industrial supply companies like McMaster-Carr or Grainger for "brass swivel hose barb NPT" or contact your local hydraulic shop. They often stock specialty brass fittings that aren't available at typical RV or home improvement stores.