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What Makes the H2O Pitless Unit Unique? Inside Merrill’s Reengineered Components
When it comes to protecting your water system investment, cutting corners is not an option. That's why water well professionals across North America trust Merrill’s H2O Pitless Control Units—a solution built not just to meet code, but to exceed expectations. Engineered from the ground up for reliability, ease of maintenance, and long-term value, Merrill’s H2O Unit combines smart design with rugged materials, offering an all-in-one pump control package inside a 12-inch casing.
Let’s dive into what makes our H2O Pitless Unit stand out from the rest—and why it’s fast becoming a favorite among wholesalers, contractors, and well drillers.
Engineered for Easy Installation, Service, and Code Compliance
Our H2O Pitless Units are available with galvanized or PVC upper casing, and connect directly to 4", 5", 6", or 8" well casings. At the top sits a 12” casing—a spacious, weather-sealed chamber that contains everything from the expansion tank to the VFD (variable frequency drive) mount.
✅ Benefit: Fewer trips down the well, less time on site, and easy compliance with state and health department codes (including Wisconsin DNR and Minnesota DOH approvals).

Inside the Innovation: Reengineered Internal Components
What truly sets the H2O Unit apart is what’s on the inside:
✔️ Universal VFD Mounting Plate
A marine-grade aluminum mounting plate is built into the 12” watertight cap, allowing you to mount your VFD drive (any USA Pump Co.) right at the wellhead.
✔️ Integrated Expansion Tank
We include an internal 2.1, 4.5, or 6-gallon pre-pressurized tank (set at 35 PSI) that’s corrosion-resistant and long-lasting.
Smart Design Tip: All fittings and controls are pre-planned to fit inside a 12” casing—no guesswork or field modifications needed.
✔️ Built-in Pull Strap
Need to service the well? No problem. A built-in galvanized steel pull strap means the entire control unit can be removed without special tools.
Now Available with Full Stainless Steel Component Option
New for 2025, Merrill now offers an upgraded Stainless Steel Package for high-corrosion environments or customers who demand the best in durability:
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1-1/4” Stainless Steel Female Valve
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1-1/4” Pull Pipe Stainless Steel Male Valve
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Heavy-Duty Stainless Steel Pitless Adapter
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Stainless Steel Cross & Nipple
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Stainless Steel Hardware Throughout
This reengineered stainless upgrade is ideal for high-acidity soils or systems where longevity and zero lead content are top priorities.

Pressure Switch Control—At the Wellhead
Eliminate the control box. With Merrill’s H2O Pressure Switch Control Package, your pressure switch, expansion tank, and all control fittings fit cleanly inside the casing. Designed for use with a 6-gallon tank or larger, this all-in-one setup saves both space and installation time.
Included in the package:
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Stainless steel clamps & tubing
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No-lead brass fittings
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Pressure switch bracket
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Cycle Stop Valve
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Optional: Merrill MPSXHD or MCSHD pressure switches rated up to 5 HP
Fully Code-Compliant & Lead-Free
All Merrill H2O units are constructed with:
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No-lead brass waterways
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Pitless adapters that meet NSF/ANSI/CAN 61 and 372
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Lead-free pressure tanks with stainless steel fittings
This makes them safe for residential and potable water applications, helping you and your customers stay compliant and confident.
Sizing & Compatibility
Merrill’s H2O Pitless Units are available in multiple configurations:
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Casing Sizes: 4", 5", 6", or 8"
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Bury Depths: 3' to 7'
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Tank Sizes: No tank, 2.1, 4.5, or 6 gallons
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Discharge Sizes: 1", 1-1/4", or 2"
Need help selecting the right configuration? Our expert team is always here to help.
Built with the Installer in Mind
Every detail is designed for faster installs, easier service, and fewer callbacks.
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All parts pre-tapped for transducer, gauge, and relief valve
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Pull strap makes removal easy—no hoists required
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Units come preassembled, watertight, and ready for action
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Durable vent screens, gaskets, and o-rings included
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Compatible with Merrill’s APC Pitless Connectors for quick casing adaptation
Learn More & See It in Action
Want to dig deeper or see how easy installation really is? We’ve got you covered:
👉 Download the Full H2O Pitless Unit Brochure (PDF)
Explore models, part numbers, materials, tank sizes, and specifications for every casing diameter.
Explore models, part numbers, materials, tank sizes, and specifications for every casing diameter.
👉 Watch: Easy Guide – How to Install the Merrill H2O Pitless Control Unit
See the step-by-step process in action, from casing prep to final cap—filmed on an actual job site.
See the step-by-step process in action, from casing prep to final cap—filmed on an actual job site.
👉 Driller's Review – Why Water Well Pros Prefer This Unit
Hear directly from contractors who trust Merrill’s H2O Pitless Unit for their toughest installs and demanding climates.
Hear directly from contractors who trust Merrill’s H2O Pitless Unit for their toughest installs and demanding climates.

Why Choose Merrill?
With over 75 years of industry experience, Merrill has built its reputation on engineering excellence, industry certifications, and customer service. The H2O Pitless Unit is a reflection of that commitment—trusted by professionals who know quality when they see it.
📞 Ready to order or get help? Contact us at (800) 831-6962 or visit merrillmfg.com
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