Seven Pipes to Two: The Case for Integrated Piping Systems

The Seven-Pipe Problem

A conventional hydronic HVAC installation requires seven discrete pipe runs: chilled water supply, chilled water return, hot water supply, hot water return, domestic hot water supply, domestic hot water recirculation, and domestic cold water. Each run demands its own supports, insulation, penetrations, isolation valves, and—critically—joints. Every joint is a potential leak point. Every penetration is a potential fire stop failure. Every foot of insulation is labor and material cost that compounds across a building’s vertical rise.

In a 25-story multifamily tower, this configuration translates to thousands of linear feet of pipe, hundreds of hangers, and dozens of isolation valves per riser. The maintenance burden scales accordingly: more components mean more failure modes, more spare parts inventory, and more technician hours spent diagnosing which of seven systems is the source of a pressure anomaly or temperature complaint.

How IPS Consolidates to Two

Williams’ Integrated Piping System takes a different approach. Instead of maintaining separate hydronic loops for heating and cooling alongside domestic water lines, IPS uses the domestic hot and cold water supply as the thermal distribution medium. Two constantly circulating water lines—domestic hot and domestic cold—serve both HVAC and potable water functions simultaneously.

The system delivers heating and cooling through fan coil units that are NSF/ANSI 61 and 372 certified for potable water contact.¹ These units use seamless copper tubes mechanically expanded into aluminum fins, housed in powder-coated steel cabinets rated for 1,500-hour salt spray testing per ASTM-B117.² The coils are hydrostatically tested to 350 PSIG and rated for 300 PSIG maximum working pressure at 200°F.²

The consolidation is not merely a reduction in pipe count—it eliminates the need for dedicated chilled water and hot water mechanical plants serving the comfort system. The domestic water heater and chiller serve double duty, and the distribution piping serves both domestic and comfort loads.

The Certification Framework

The safety case for running HVAC loads through potable water lines rests on third-party certification. NSF/ANSI 372 defines “lead free” as not more than 0.25% lead calculated as a weighted average across wetted surfaces, with solder and flux limited to 0.2% lead.³ NSF/ANSI 61 governs what actually leaches into the water—endpoint devices must now meet a Q-value limit of 1.0 micrograms, reduced from 5.0 micrograms in 2024.⁴

Williams fan coils carry both certifications. The piping itself—copper, 304 stainless steel, or polypropylene for mains; copper, stainless, polypropylene, or PEX for fixtures—must also meet potable water standards.² The control valves (TRACvalve, rated 130 PSI close-off with 300:1 rangeability) and the BACNet BTL-certified control system complete the package.²

Competitive System Analysis

The decision to use IPS is typically made against five alternatives: PTAC, two-pipe hydronic, four-pipe hydronic, VRF, and water-source heat pumps. Each has trade-offs that become clear when evaluated against lifecycle cost rather than first cost alone.

PTAC units offer the lowest first cost but the shortest lifespan. ASHRAE equipment life data shows commercial through-the-wall units at 15 years median life, with industry sources citing 7-15 years depending on maintenance.⁵ ⁶ PTACs also introduce noise directly into the occupied space and require exterior wall penetrations that complicate building envelope design.

Two-pipe hydronic systems cannot heat and cool simultaneously. In a building where south-facing units need cooling while north-facing units need heating—a common condition in swing seasons—two-pipe systems force building-wide mode selection. This creates comfort complaints that no amount of equipment capacity can resolve.

Four-pipe hydronic systems solve the simultaneous heating/cooling problem but at the cost of complexity. Adding the four-pipe hydronic distribution to the three domestic water lines yields the seven-pipe configuration that IPS eliminates.

VRF (Variable Refrigerant Flow) heat pumps have gained market share for their zoning flexibility, but they carry two significant liabilities. First, cold-climate performance degrades substantially: standard VRF capacity drops to as low as 70% of rated output at 5°F outdoor temperature, and heating season efficiency runs approximately 30% below rated values.⁷ ⁸ Second, VRF systems distribute refrigerant throughout the building, creating long-term regulatory exposure as HFC phasedowns accelerate.

Water-source heat pumps perform well but place compressors in or near occupied spaces, introducing maintenance access challenges and noise concerns.

The Refrigerant Regulatory Shift

The AIM Act of 2020 mandates an 85% reduction in HFC production and consumption by 2036, measured against 2011-2013 baseline levels.⁹ The phasedown is already in progress: 2024-2028 allows only 60% of baseline, dropping to 30% for 2029-2033.⁹

R-410A, the dominant refrigerant in VRF and split-system equipment, carries a Global Warming Potential of 2,088—meaning each pound released has 2,088 times the warming impact of a pound of CO₂ over 100 years.¹⁰ The EPA’s 2025 GWP limit for air conditioning and heat pump equipment is 700, which R-410A exceeds by a factor of three.¹¹

For building owners evaluating 20-year lifecycle costs, this regulatory trajectory introduces significant uncertainty into any system that depends on high-GWP refrigerants distributed throughout the building. IPS, which uses water as the distribution medium and confines refrigerant to central plant equipment, sidesteps this exposure.

Equipment Lifespan Comparison

ASHRAE equipment life expectancy data shows hydronic fan coil units at 20 years median service life.⁵ This compares favorably to:

• Commercial through-the-wall AC (PTAC): 15 years
• Window units: 10 years
• Commercial water-to-air heat pumps: 19 years

The difference compounds over a building’s 50-year economic life. A PTAC-based system will require three or four equipment replacement cycles; a hydronic fan coil system will require two or three. Each replacement cycle involves not just equipment cost but tenant disruption, construction management, and the risk of collateral damage to finishes.

Project Evidence

Three completed projects illustrate IPS implementation across building types:

Hewing Hotel, Minneapolis: A 124-room boutique hotel in a 126-year-old, 116,000-square-foot building. The $38 million renovation required a system capable of simultaneous heating and cooling (Minneapolis weather swings demand this), quiet operation for guest comfort, and compatibility with historic building constraints. The team evaluated WSHP, two-pipe, four-pipe, PTAC, and VRF before selecting IPS.¹²

The Atlantic, Philadelphia: A 25-story, 270-unit multifamily tower. The mechanical plant includes a 750-ton cooling tower, two 375-ton compressors, three condensing boilers, a 120°F storage tank, and two 300 PSI plate-and-frame heat exchangers. Hydronic distribution uses 3-inch to 10-inch 304 stainless steel piping, all NSF 61 certified.¹³

Mariposa, Denver: A 900-unit, 1.2-million-square-foot mixed-income community across 34 buildings developed by Denver Housing Authority as a HOPE VI project. The phased development allowed a direct comparison: multiple system types were installed across different phases, with IPS selected for Phases III and VI based on performance data from earlier phases.¹⁴

Implications

The case for IPS rests on three engineering arguments:

First, fewer pipes mean fewer failure points. Every joint, valve, and penetration eliminated is a leak that will never happen and a maintenance task that will never be scheduled.

Second, equipment longevity favors hydronic over DX. Twenty-year median life for fan coils versus 10-15 years for PTACs and packaged equipment translates directly to lower lifecycle cost.

Third, regulatory risk favors water over refrigerant as a distribution medium. The AIM Act phasedown is not speculation—it is law, with defined percentage reductions through 2036 and beyond.

For facility managers and developers evaluating HVAC options, the question is not whether IPS costs more or less than alternatives at installation. The question is what the total cost of ownership looks like across a 20-year analysis period when equipment replacement cycles, maintenance labor, and refrigerant regulatory compliance are included in the model.

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Works Cited

1. NSF/ANSI 61 and 372 Certification Requirements, ANSI Blog, accessed February 2025, https://blog.ansi.org/ansi/lead-drinking-water-regulations-nsf-ansi-372/
2. Williams Comfort Products, Integrated Piping System Technical Specifications, accessed February 2025, https://williamscomfort.com/products/commercial-hvac-systems/integrated-piping-system-ips/
3. Safe Drinking Water Act Lead Free Requirements, NSF International, accessed February 2025, https://www.nsf.org/news/plumbing-standard-revisions-tighten-lead-leaching-criteria-drinking-water
4. NSF 61 vs NSF 372 Comparison, Merit Brass, accessed February 2025, https://meritbrass.com/blog/nsf-61-vs-nsf-372
5. ASHRAE Equipment Life Expectancy Chart, ASHRAE Handbook—HVAC Applications, accessed February 2025, https://pdf4pro.com/view/ashrae-equipment-life-expectancy-chart-6313fb.html
6. Average Lifespan of PTAC Units, Cool Penguin AACS, accessed February 2025, https://www.coolpenguinaacs.com/blog-news/average-lifespan-ptac-units
7. Advanced Heating Technologies for VRF, Construction Specifier, accessed February 2025, https://www.constructionspecifier.com/advanced-heating-technologies-for-vrf/2/
8. Cold Climate VRF Systems, Slipstream Research, accessed February 2025, https://slipstreaminc.org/research/cold-climate-vrf-systems
9. EPA Frequent Questions on Phasedown of Hydrofluorocarbons, EPA, accessed February 2025, https://www.epa.gov/climate-hfcs-reduction/frequent-questions-phasedown-hydrofluorocarbons
10. Technology Transitions GWP Reference Table, EPA, accessed February 2025, https://www.epa.gov/climate-hfcs-reduction/technology-transitions-gwp-reference-table
11. Global Warming Potential Explained, Trane, accessed February 2025, https://www.trane.com/residential/en/resources/glossary/gwp-meaning/
12. Williams IPS Selected for Hewing Hotel Renovation, Williams Comfort Products, accessed February 2025, https://williamscomfort.com/products/hydronic-systems/integrated-piping-system-ips/hewing-hotel/
13. Williams Integrated Piping System (IPS) at The Atlantic in Philadelphia, PA, Williams Comfort Products, accessed February 2025, https://williamscomfort.com/products/hydronic-systems/integrated-piping-system-ips/the-atlantic-in-philadelphia-pa/
14. Integrated Piping System Outperforms in Denver (Mariposa), Williams Comfort Products, accessed February 2025, https://williamscomfort.com/products/hydronic-systems/integrated-piping-system-ips/integrated-piping-system-outperforms/