Insert Fitting Guide
What Insert Fitting Do I Need?
Match the fitting style, poly pipe size, thread, material, and clamp—without guessing.
- Insert side: Fits poly pipe
- Thread side: Connects to the next component
- Hose clamp: Secures the pipe
STEP 1: CHOOSE THE FITTING STYLE
What Are You Connecting?
Start with the connection you need to make. Each insert fitting style solves a different job.
Male Adapter
Connects poly pipe to a female-threaded port.
Shop Male Adapters
Female Adapter
Connects poly pipe to a male-threaded fitting or port.
Shop Female Adapters
Insert Coupling
Joins two sections of poly pipe in a straight line.
Shop Insert Couplings
Insert Elbow
Changes the direction of the water line 90 degrees.
Shop Insert Elbows
Insert Tee
Creates a branch from the main water line.
Shop Insert Tees
Union Adapter
Adds a removable connection for easier servicing or disconnection.
Shop Union Adapters
STEP 2: READ THE FITTING SIZE
How Do You Read an Insert Fitting Size?
Some fittings are insert × insert. Others are insert × thread. Read each side before ordering.
1" Insert × 1" MIP
- 1" Insert — matches the nominal poly pipe size
- 1" — thread size
- MIP — male pipe thread
1" Insert × 1" Insert
Joins two sections of 1" poly pipe.
1" Insert × 1" FIP
Fits 1" poly pipe and accepts a 1" male-threaded connection.
- Insert
- Barbed connection matched to the nominal poly-pipe size.
- MIP
- External male threads.
- FIP
- Internal female threads.
Check every opening. A fitting can match your poly pipe but still have the wrong thread type, thread size, or connection type.
STEP 3: MATCH THE POLY PIPE
What Size Insert Fitting Fits My Poly Pipe?
Confirm the pipe is compatible polyethylene water pipe, then match its printed nominal size to the fitting’s listed Plastic Pipe Insert Size.
1" Poly Pipe → 1" Insert Fitting
Common Insert Sizes
- 1/2"
- 3/4"
- 1"
- 1-1/4"
- 1-1/2"
- 2"
Additional sizes are available on select Merrill fittings.
Do not choose by appearance alone. Confirm the pipe type and nominal size, then match both to the product specifications before ordering.
STEP 4: CHOOSE THE MATERIAL
Which Material Fits Your Installation?
Material affects corrosion resistance, durability, and cost. Start with where and how the fitting will be used.
Buried or Hard to Access
Consider stainless steel or no-lead bronze for durable, corrosion-resistant connections.
Common Water-System Connection
No-lead brass is a dependable choice for many standard applications.
Economical or Standard Application
Zinc-plated steel, nylon, PVC, and polyethylene offer lower-cost choices for suitable installations.
Always confirm the product material is approved for your intended water system and installation.
STEP 5: ADD THE HOSE CLAMP
Do Barbed Insert Fittings Need Hose Clamps?
Yes. Flexible poly pipe should be secured over each insert barb with a properly sized hose clamp.
Match the clamp size
Confirm the clamp range fits your pipe and fitting.
Secure every connected barb
Each barbed end connected to poly pipe needs to be secured.
Order clamps separately
Do not assume hose clamps are included with the fitting.
Check the fitting and clamp product pages before ordering. Do not choose the clamp by appearance alone.
Check before ordering
Final Fit Check
Before ordering, confirm the details that apply to your fitting.
- Fitting style
- Poly pipe insert size
- Thread type and size, if applicable
- Material and intended use
- Hose clamp size
Combination or reducing fitting? Confirm the size and connection type at every opening.
Include a properly sized hose clamp for every insert barb connected to flexible poly pipe.
BEFORE YOU ORDER
Common Insert Fitting Questions
What if I cannot identify my poly pipe size?
Check the size printed on the pipe and match it to the fitting’s listed insert size. Do not choose by appearance alone. Contact Merrill or a qualified professional if the pipe cannot be confidently identified.
Do Insert Fittings Need Hose Clamps?
Yes. Barbed insert fittings used with flexible poly pipe should be secured with a properly sized hose clamp. Match the clamp range to your pipe size and confirm the fitting and clamp specifications before ordering.
When should I call a professional?
Call a qualified professional when buried water lines, pumps, damaged piping, system pressure, or product compatibility cannot be safely confirmed.
Ready to Make the Right Connection?
Choose the insert fitting that matches your pipe, thread, and installation.
Still unsure? Review Fitting Styles