How much does a missed call cost a Chattanooga plumber? The per-call math, the 423-area-code overlay, what changes when a recovered-call layer is in place.

Step through the per-call formula with a working-average 423-area-code plumbing shop — roughly 50 inbound calls a week, about 25% missing a live person on the first ring, and the $480 plumbing average ticket the /plumbing/calculator defaults to — and the math lands on ~$14,309 of monthly recoverable revenue. That is the upper bound on what a fully clean recovery layer could put back on the dispatch board; a real shop typically nets somewhere under that figure, and an under-tuned one nets much less.

The full formula is the same one the rest of the funnel runs against: weeklyCalls × missedRate × CLOSE_RATE_DEFAULT × avgTicket, carried across the 4.33 weeks/month constant the per-shop worked example also uses. The exact per-shop number shifts with how heavy the after-hours mix is on the missed-call share, but the shape is the same — and every line item in the formula is a number that comes out of the call log and ticket history the audit-request intake reads.

Plumbing carries the lowest average ticket of the three trades the trade pages publish — $480 versus $720 for HVAC and $880 for electrical — but it also carries the most after-hours volume, which is what makes the per-call number land where it does on the same dispatch board.

• 50 weekly calls is a working-average plumbing shapeSome shops run 30, some run 200. The /plumbing/calculator lets you punch in your own volume; the trade-specific calculator defaults to the plumbing working-average. Either way the formula is identical.
• 25% miss rate is a working average across the tradesThe miss rate moves around — a one-dispatcher shop on a busy Tuesday can run closer to 35–40% for that hour; a fully-staffed two-line office on a quiet Wednesday can run below 10%. Use 25% as the anchor, then stress-test the calculator against your own call log.
• A 55% close rate is built into the math as a constantThe close rate on a recovered call is held at 55% (CLOSE_RATE_DEFAULT) and is not exposed as a knob. That mirrors what the per-shop audit sees across the trades; it is conservative for warm leads and generous for cold ones, so it does not skew the answer either way.
• $480 average ticket sits in the plumbing $350–500 bandPlumbing shops cluster their jobs inside the $350–500 band, so the /plumbing/calculator and the generic /calculator both default to $480 — the same number the /plumbing proof row publishes. The after-hours premium jobs (water-heater swaps, sewer back-ups, burst-pipe calls) lift the average above the mid-band.

The per-call formula is generic; the per-call number lands where it does because of what the Chattanooga plumbing market looks like. Most of the 423-area-code trades a Holdfast audit sees are residential plumbing shops whose after-hours share runs above 30% — burst pipes at 11pm, water-heater swaps before the morning crew is on the road, sewer back-ups through the weekend. That after-hours volume is what makes the missed-call layer hardest to staff by hand; the dispatcher would be asleep for most of the volume the recovery layer is built to catch.

Three things shape the overlay. First, the 423 area code covers a wide service-area geometry — Signal Mountain, Hixson, Ooltewah, East Ridge, and Lookout Mountain — and the dispatcher is rarely sitting next to the same physical call list the office answers. Second, the after-hours mix is disproportionately composed of the high-ticket emergency jobs (water-heater swaps, sewer back-ups, burst-pipe repairs) that lift the average ticket well above the mid-band. Third, the next-shop-around dynamics on weekends run hot — a Saturday-morning burst-pipe call that misses the shop is a call another plumbing shop is happy to answer.

The overlay is what an install tunes against, and it is what the audit-request intake walks when an owner-operator starts the conversation. The same overlay shows up on /chattanooga — three trade verticals under one after-hours recovery layer — and on /plumbing in the proof bullets the calculator leans on. The numbers above are not invented stats; they are the working averages the install is tuned against, drawn from the per-trade proof points and re-used on the per-trade routed calculators so the starting average ticket is the same number the trade page is published with.

• 30% after-hours share · PlumbingRoughly three in ten inbound plumbing calls land outside office hours. That is the recovery layer we get paid for — the calls the dispatcher would have missed asleep. Same shape as the after-hours war stories on /plumbing.
• After-hours premium jobs lift the average ticketWater-heater swaps, sewer back-ups, and burst-pipe repairs pull the average ticket above the $480 mid-band default on a working week. The /plumbing/calculator defaults to $480 for the same reason — the published mid-band, not the after-hours lift, sets the anchor.
• 423 area-code service-area geometryA wide residential footprint — Signal Mountain, Hixson, Ooltewah, East Ridge, Lookout Mountain — and a dispatcher who is rarely sitting next to the line the office just answered. Same shape the /chattanooga service-area page covers.
• After-hours emergencies run high-ticketThe weekend burst-pipe call, the Friday water-heater swap, the Sunday sewer-line diagnostic — the same calls that push the after-hours share above 30% are the same ones that pull the per-job economics above the cross-trade $620.

Once a recovered-call layer is in place, three things shift on the dispatch board. First, the same per-call math that lands at ~$14,309/mo for a working-average Chattanooga plumber becomes a per-shop worksheet — the audit-request intake pulls ten of your recent inbound calls and your last quarter's ticket values to fill the same inputs from real numbers. Second, the after-hours slot the dispatcher would have missed asleep is a confirmed booking on the dispatch board before the morning crew is on the road — same shape as the 3-touch SMS cadence and the booking handoff the playbook on /resources/missed-call-recovery-playbook walks.

Third, the dispatcher load shifts from 'catch as many calls as the office can answer' to 'work the bookings the recovery layer has already qualified' — the per-shop shape the audit pulls ten recent recordings against. The cross-trade averages the per-call math leans on are what carry the formula into a defensible monthly figure for your vertical; the per-shop numbers your own call log produces are what the audit writes back into the same sheet.

The two worked projections on /case-studies — a 3-truck plumbing shop and a 4-tech HVAC shop — walk the same per-shop sheet with the same cross-trade averages, with the monthly recovery figure tuned to a real-shape shop's weekly call volume. Both are labeled as samples; the audit is the path to the shop's own numbers.

• Confirmed bookings on the dispatch boardThe 3-touch SMS cadence and the booking handoff on /resources/missed-call-recovery-playbook turn the recovered-call slot into a confirmed job on whichever dispatch board the shop already runs — ServiceTitan, Housecall Pro, or Jobber.
• After-hours coverage the dispatcher can sleep throughThe after-hours premium jobs that drive the recovery numbers are the same ones the dispatcher would have missed asleep — the recovery layer is the front-desk-of-record for those calls, not a side-channel sideboard.
• A per-shop sheet the audit fills from your call logA 20-minute audit uses ten of your recent inbound recordings and your last quarter's ticket values to fill the same inputs from real numbers — same shape, real inputs, sent back within a few days.
• Sample projections on /case-studiesThe two worked projections on /case-studies — a 3-truck plumbing shop (~$11,200/mo) and a 4-tech HVAC shop (~$16,200/mo) — walk the same per-shop sheet for real-shape shops. Both labeled as samples; the audit is the path to your own numbers.