Pumped from aquifers lodged within porous rock, and funneled to Oahu faucets through a vast network of wells, tunnels and mains, groundwater provides nearly every drop of our drinking water. Most of us pay little attention to our everyday dependence on the system — until flow is interrupted by a main break.

When a break occurs in a high-traffic area — such as in January 2017, when a 24-inch line ruptured near where the H-1 merges into Kalanianaole Highway — several days can pass before water-related problems, including roadway backups, are alleviated.

Such incidents serve as reminders that largely out of sight are some 2,100 miles of pipe delivering water to us. Another reminder — this one focused on aging pipe — is now surfacing as Honolulu Board of Water Supply (BWS) pitches proposed rate hikes for municipal water.

The semi-autonomous agency board voted this week to seek public feedback on a draft package of hikes — 12.5 percent over four years, with increases starting in mid-2019. BWS, which relies on customer charges to pay all expenses tied to system upkeep, says the bump is needed to fund a stepped-up effort to upgrade its system by replacing 21 miles of pipe a year over the next 10 years — about double its current replacement pace.

While no customer wants to see rates rise, the proposal rightly reserves higher-than-average increases for larger residential users in single-family homes. Residential customers using the least would see a relatively small increase or, possibly, a decrease. That seems fair — partly because conservation should be rewarded, even in green Hawaii, where water shortages and land subsidence touched off by drained groundwater supplies are not front-and-center concerns.

The last time BWS put in place a set of rate increases, they spanned a decade, starting in 2006. The previous increase had been in the mid-1990s. The interim lull resulted in a backlog of deferred system upgrades. BWS responded by deploying drastic “rate shocks,” starting with a 50 percent increase over five years, followed by a 70 percent hike over the subsequent five years.

The jarring effect was exacerbated when a plan to put in a new customer care and billing system caused the agency to “back-bill” a number of its customers, resulting in confusing spikes in water bills, and contributing to the eventual cost of the accounting system skyrocketing to more than three times its original price tag. A 2014 city audit concluded that the water board had “inadequately planned for its utility customer billing information system implementation,” a switch activated in 2013 with an initial cost set at $5 million.

This time around, it appears that BWS is building its case for hikes on a four-year analysis of lessons learned. Let’s hope so, anyway. The analysis involved stakeholder scrutiny of a 10-year projection for maintaining and improving operations. The probe will continue this month and in May, with public hearings in Honolulu, Kapolei, Kaneohe and Mililani.

In addition to suggested changes that should be welcome, such as the addition of new green-minded “affordability” tiers and and a more precise billing charge (based on meter size rather than a flat rate), BWS wants to put in place a structural shift through which single-family residences would see a more substantial bill increase than multifamily residences.

The move appears to make sense as a fair-share tweak. Currently, single-family households pay 88 percent of the costs to serve them, with multi-unit customers (triplexes up to high-rise complexes) subsidizing much of the balance. The imbalance should be corrected.

Few things are as essential to daily living as reliable water service. A carefully charted and thoroughly vetted BWS plan holds potential to serve as a much-needed guide to navigating the next decade’s delivery in Oahu’s biggest public water system, which serves about 1 million customers.