As some of the biggest zoning reforms in decades take effect across New Hampshire, a new issue is quickly coming into focus: access to water and sewer infrastructure. Recent data released by the St. Anselm College-backed New Hampshire Zoning Atlas shows that a surprisingly small percentage of the state’s “buildable land” is actually connected to public water or sewer services — raising serious questions about where new homes can realistically be built, even in areas with permissive zoning.

What the Data Says — and Why It Matters

• According to the updated Zoning Atlas, only about 12% of New Hampshire’s buildable land has access to either public water or sewer service.
• Even more telling: just 5.6% of buildable parcels have access to both water and sewer — the combination often required for higher-density or multi-unit housing.

These statistics represent a major structural constraint. As one construction-management executive put it at a recent presentation: “When we talk about density … there are really two major determining factors … One is zoning, and the other is the availability of sewer and water.” 

What this shows is that loosening zoning laws — allowing more density, ADUs, or multifamily housing — won’t automatically lead to more buildable homes unless infrastructure keeps pace. For many parcels, “buildable on paper” does not mean “buildable with utilities.”

Infrastructure — Not Just Zoning — Determines What Gets Built

Advocates and municipal leaders are sounding the alarm: public water and sewer systems in many towns are already aging, operating near capacity, or limited by natural constraints (groundwater availability, environmental regulations, wastewater treatment capacity). Expanding that infrastructure is expensive and complicated. 

Some potential solutions are being floated. In areas where traditional septic systems won’t cut it — poor soils, high density, groundwater limitations — alternatives might include aerobic treatment systems, or community-scale septic systems designed to serve multiple units. These could open up more land for safe development, but they come with their own costs and regulatory hurdles.

Municipalities themselves face tough choices. As one town official noted, even parcels already connected to public water/sewer aren’t necessarily “easy wins”: just having lines in place doesn’t guarantee enough capacity for more housing. Upgrades — new pipes, widened mains, expanded treatment plants — may be required before a single additional home can be safely connected. 

What This Means for Key Stakeholders

For Realtors & Developers

• Due diligence just got more complex. Before treating a parcel as “ready to build,” you’ll now need to verify not just zoning, but water/sewer availability and capacity. A flashy zoning map doesn’t mean much without matching infrastructure.
  
  
• Infrastructure-ready parcels will command a premium. Land that already sits on functioning mains — especially on both water and sewer — becomes more valuable. These sites may out-compete others even if zoning is equivalent.
  
  
• Long-term planning may tilt toward infrastructure investment. Some of the next successful developments might be in places that can drive or fund infrastructure — or where municipal authorities are willing to expand lines for growth.

For Municipalities and Local Governments

• Zoning reform is necessary, but not sufficient. Municipalities who support growth must also plan for infrastructure — water supply, wastewater treatment, pipe maintenance, and expansion. Without that, housing goals could stall.
  
  
• Public funding or bonding may become inevitable. Expanding municipal water/sewer systems will likely require significant funds. Some towns may need to ask voters to approve municipal bonds or special assessments — at a time when many residents feel taxed heavily already.
  
  
• Alternative wastewater solutions should get more attention. For rural or semi-rural areas unwilling or unable to support traditional infrastructure expansion, community septic or advanced treatment systems may offer a middle path.

For Homeowners & Communities

• Growth may become more concentrated. Expect new housing developments to gravitate toward areas with existing water/sewer — not necessarily where zoning is most permissive or land is cheapest.
  
  
• Potential trade-offs: density vs. infrastructure cost. Where growth happens, towns may face rising costs (infrastructure upgrades, maintenance, environmental compliance). This could bring pushback from residents who worry about taxes, the environment, or changes to community character.
  
  
• Long-term value may shift. As infrastructure becomes the gatekeeper for new housing, homes and parcels with good water/sewer access may increase in value — while raw, unserviced lots may struggle to attract investment.

What’s Next (and What to Watch)

• Several lawmakers are reportedly preparing bills for the 2026 session to address infrastructure — expansion of water and sewer services, even establishing mechanisms like special-assessment districts to help towns fund upgrades.
  
  
• The Zoning Atlas provides a new transparency tool: developers, planners, and citizens can now visually map where water/sewer exists statewide — and where it doesn’t. That data will likely shape which areas get attention for future growth.
  
  
• Expect increasing debate at local and state levels about balancing housing needs with infrastructure limits and the costs of expansion.

Overall Implication

New Hampshire’s housing challenge runs deeper than zoning. The new water and sewer-access data shows that infrastructure — not just permissive rules — may be the biggest constraint on where new homes can go. For anyone involved in real estate, planning, or local government, that means rethinking assumptions: availability of water/sewer will increasingly define where development is realistic — and where it isn’t.