220 Beds, One Cooling Tower, and a 24% Fixture Package

Scope: the calculation covers the fixtures, fittings, and appliances enumerated in the credit - water closets, urinals, lavatory and kitchen faucets, showers, pre-rinse spray valves, and clothes washers and dishwashers where provided by the project. It is a weighted comparison by fixture type and occupant use group, done in the calculator.

What does not count: cooling tower makeup, sterilization and other process water, and irrigation. Those are addressed by different credits. So the headline 12 million gallon figure is misleading - the prerequisite is measured against the 45% fixture slice only.

Does 24% clear the prerequisite? Yes. The prerequisite threshold is a 20% reduction; the credit then steps up in tiers, so 24% earns the prerequisite plus the first credit tier, and the next tiers require 25%, 30%, 35% and beyond. Two cautions:

• Verify the baseline is built from the correct fixture counts and occupancies. Hospitals are frequently mis-entered - patient rooms, staff lockers, and public restrooms have very different use group assumptions, and errors here can swamp a real 4-point improvement.
• Do not chase the next tier inside patient care areas. The infection control committee's review will cost more schedule than the tier is worth, and low-flow fixtures in a hospital carry a stagnation and biofilm risk that belongs in the water management plan, not the credit calculator.

1. Water metering - cheapest point on the board. Permanent meters on the building's water supply and on each subsystem (indoor plumbing, irrigation, cooling tower, any reclaimed water) is a specification edit and a few thousand dollars of hardware. No design change, no risk. Take it first.

2. Cooling tower - the big water volume, and a real engineering question. This is the largest non-fixture use at 25% of 12 million gallons, and the current design at three cycles is throwing away most of it. Run a cycles-of-concentration analysis against the actual makeup water quality (the credit's limits are tied to specific parameters - calcium, alkalinity, silica, chloride, conductivity - not a generic hardness number):

• At 180 mg/L hardness, a treatment program with scale and biological inhibition plus side-stream filtration can plausibly push the tower to five or six cycles. The water savings scale roughly as (cycles − 1)/cycles: going from 3 to 6 cycles cuts blowdown from 50% to 20% of evaporation, i.e., a 60% reduction in that load.
• The counter-risk is scaling, corrosion, and biological growth. If the analysis says the makeup water chemistry cannot support the higher cycles without softening, the softening itself consumes water and salt - model the net, not the gross.

3. Irrigation - possibly free. At only 10% of use, converting ornamental turf to native and adapted planting may allow eliminating the permanent irrigation system altogether, which is simple, cheap, and eliminates a maintenance liability in a drought region. Check whether the municipal restriction already caps irrigation.

Ranking logic for the owner: metering first (certain, cheap), irrigation second (likely elimination, low cost), cooling tower third (largest volume, but requires a treatment design, a maintenance contract, and a commissioning check).

Treat water safety as a design constraint, not an objection to efficiency. They are compatible, but only if the system is designed and operated for it.

Domestic water. Low-flow fixtures reduce volume and velocity, which means longer residence time and more opportunity for biofilm in dead legs - a known problem in hospitals with seasonal occupancy swings (closed wings, low-census floors). The water management plan should specify:

• Hot water return loops and thermostatic mixing valves at points of use, with hot water maintained at temperature throughout.
• A flushing protocol for low-use areas and for any wing taken out of service.
• Sampling points at distal outlets.

The ASHRAE 188 water management program is expected practice for a hospital regardless of LEED, and its existence is a strong point in a certification narrative. Do not let a two-point fixture upgrade create a wing that nobody can safely reopen.

Cooling tower. Pushing cycles of concentration increases dissolved solids and temperature-driven biological risk in the tower, which is the classic Legionella amplification site. The treatment program, drift eliminators, and access for cleaning are part of the design, not an afterthought. If the owner will not fund a treatment contract, do not claim the higher cycles - the savings are not real if the tower has to be dumped and cleaned twice a year.

Message to the owner: the efficiency strategy is defensible and worth real points, but two of the three measures (cooling tower and anything touching patient fixtures) require operational commitments that outlast construction. Get the facilities director in the room before the credits are locked, because they, not the design team, will be held to them.