Single Well, No Backup: A Pump Failure With 60 Residents on Storage
You run a 60-connection community water system with one well (rated 30 gpm), one 10,000-gallon storage tank, and no intertie or backup source. The well pump fails on a Friday afternoon; you cannot get a replacement until Monday. Current tank level is 7,200 gallons. Average demand is about 55 gallons per connection per day, but peak-hour demand runs at roughly 2.5 times the average hourly rate between 6 and 9 a.m. Your state requires you to notify the primacy agency of any loss of source or pressure and to issue a public notice if you cannot maintain pressure. You have a portable generator, a spare booster pump, and one operator (you).
1. Calculate how long your stored water will last under average demand and under a realistic peak, and decide whether you can avoid a boil-water notice.
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Average demand: 60 connections x 55 gal/day = 3,300 gal/day, or ~137.5 gal/hr average. Stored usable volume - assume you must keep a residual for fire and pressure, say 1,000 gal minimum - so usable is ~6,200 gal. At 137.5 gal/hr, that lasts ~45 hours, which sounds like it covers the weekend.
But peak demand is the real constraint. Peak-hour rate is ~2.5 x average hourly = ~344 gal/hr for the 6–9 a.m. window. Over 3 hours that is ~1,030 gal. If the pump is down, every morning peak draws down storage faster than the average suggests. Two morning peaks (Sat, Sun) at ~1,030 gal each plus overnight base use can pull the tank toward your reserve.
Conclusion: On paper you can limp through average use, but you cannot guarantee pressure through two peak mornings with a hard 1,000-gal floor. The honest answer is that you are at real risk of losing pressure, so you should plan for a boil-water notice rather than promise you can avoid it. Notify the primacy agency immediately and document the calculation.
2. What is your sequence of actions from Friday afternoon to Monday, and what triggers a public notice?
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Friday afternoon:
- Notify the primacy agency of the source loss and your storage estimate.
- Post a precautionary notice to customers (hand-delivered or posted) explaining the situation and asking them to conserve - this buys time and is defensible.
- Check the generator and booster - confirm you can run anything critical and keep pressure on the tank.
Weekend: 4. Implement demand reduction: ask residents to limit use, defer laundry, etc. Monitor tank level at least twice daily and log it. 5. Watch for the trigger: if tank level approaches the point where you cannot hold system pressure (your 1,000-gal floor or loss of pressure anywhere), issue the boil-water notice immediately - do not wait for Monday. 6. Keep the agency informed of level trends.
Monday: 7. Install replacement pump, refill, flush, and collect bacteriological samples before lifting any notice.
The trigger for public notice is loss of pressure or inability to maintain residual, not a fixed gallon number - but you set the gallon floor in advance so you act before pressure actually drops.
3. After service is restored, what must be true before you rescind the boil-water notice?
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Rescission is a regulatory and bacteriological step, not just "the pump works again."
Requirements typically include:
- Pressure restored system-wide and held.
- Chlorine residual detectable throughout, including the far end.
- Bacteriological samples - at least two consecutive sets, collected at least 24 hours apart, all absent for total coliform and E. coli, collected after repair and flushing.
- Flushing of the system to clear any stagnant or contaminated water before sampling.
- Agency concurrence - confirm with the primacy agency that your sampling and results meet their rescission criteria before you tell customers it's safe.
Document the repair, flush volumes, residuals, and sample results. A common failure is lifting the notice on the same day the pump is fixed, before samples clear - don't do that.