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Installation Instructions for Pitless Adapter

Pitless Adapter Installation

Step 1: Pitless adapter should be installed below the frost line and on side of well casing where the supply line will run from well.

Step 2:  Center punch at selected depth setting for pitless adapter, then cut hole in casing with the appropriate size hole saw.

  • 1-3/4" Hole Saw - MB50, MBNL50, SSMB50, MB200, MBNL200, SSMB200, MBI100, MB60, MBNL60, MBNL100, MBNL100N, and MBPNL100.
  • 2-1/8" Hole Saw - MB225, MBNL225, SSMB225, MBI125, MB125N, MBNL125N, MBPNL125 and MBNL125.
  • 2-1/2" Hole Saw - MBNL250
  • 3" Hole Saw - MBNL300

Step 3: Remove the lock nut, backplate and gasket.  Do not remove the female O-Ring.  It should be installed inside well Pitless Adapter Installationcasing.

Step 4: Lower female part into hole in casing by inside male part installed upside down in female (See Figure 1 above) with a pipe attached.  The rigid pipe allows you to hold the female part in the casing, while installing the gasket, backplate and lock nut.

Step 5: Tighten lock nut before completing installation.  The backplate and lock nut should have pulled the female part and female O-Ring against the inner wall of the casing.  If necessary, the male part and pull pipe can be used for vertical alignment while tightening the lock nut.

Step 6: Remove the male part with pipe, coat machined surface and O-Ring with Anti-Seize/Gasket Lube.  Connect male part to pump drop pipe and complete installation.

Note: Merrill Manufacturing™ Pitless Adapters are designed for easier installation.

  • Factory tested at 150 PSI
  • Fits casing sizes 6" - 12"
  • Certified watertight.  Passed PAS-1

MB400 Pitless Adapter Installation Instructions

Step 1: Locate direction pipe will run from well and scribe a true vertical line on the casing at desired location.  Punch mark center of holes 3-1/4" apart.  Template can be used as a guide.

Pitless Adapter Installation

Step 2: Drill upper hole to 2-1/4" diameter and lower hole to 1-3/4" diameter.  Gasket design will allow reasonable deviation from hole roundness and size.  Deburr inner and outer edges of hole.

Step 3: Lubricate machined surface of Part (A) freely with Merrill Anti-Seize/Gasket Lube and with inner gaskets in place.  Lower into casing, using small wire in hole provided, or use ELL Part (B) by sliding into Part (A) upside down with a pipe attached.  Guide through holes in casing, attach outer gaskets and washers and wrench up nuts until all gaskets are tightened and compressed against casing.

Pitless Adapter Installation
Part (A) Slide
Pitless Adapter Installation
Part (B) ELL

Step 4: Part (B) can be assembled with necessary piping (lubricate O-Rings and machined surfaces) lowered into casing and mated with Part (A). 

Step 5: A Merrill Manufacturing™ Well Cap should be used to complete your installation.

Note: Fits all casings from 4-1/2" - 12" without changing parts.

Pitless Adapter Installation