How to Track Plumbing Parts and Inventory on the Job

Walk into the back of an average plumbing shop's service truck and you will find roughly 400-700 distinct parts: supply lines, shutoff valves, escutcheons, wax rings, copper fittings, PEX fittings, ball valves, sweat fittings, drain assemblies, faucet cartridges, water heater elements, T&P valves, pipe dope, plumber's putty, Teflon tape, hangers, straps, fasteners, and a hundred other things. The total inventory value on a well-stocked truck runs $4,000-$8,000.

Most shops have no idea what's actually on each truck at any given moment. Parts get used and not logged. Parts get pulled from the shop and not entered into the truck stock. Parts get loaned to another tech. Parts fall behind a toolbox and stay there for two years. The result is the same in nearly every shop that doesn't have a real inventory system: 6-12% of every annual parts spend is lost on the truck.

For a shop spending $80,000 a year on parts, that's $5,000-$10,000 in straight waste. This guide walks through six steps to get truck inventory under control, set the right minimum stock levels, mark parts up correctly on invoices, and audit weekly so the system stays clean.

In a shop without real parts tracking, a typical Tuesday looks like:

7:30 AM: Tech arrives at the shop, grabs three boxes of 1/2" copper couplings off the rack, throws them in the truck, doesn't tell anyone.

10:15 AM: Tech installs a new water heater, uses 6 feet of 3/4" copper pipe, two ball valves, a T&P valve, six couplings, two unions, a drip pan, and a flex line. He writes "new water heater install" on the work order. No parts list.

12:40 PM: Tech runs out of 1/2" PEX fittings on a repipe. Calls the shop. Owner drives 20 minutes to the supply house, picks up a box, drops it at the job site, charges his time and gas to nothing in particular.

3:30 PM: Tech finishes for the day. Three boxes of fittings are in the truck. He doesn't know which ones came from the shop this morning, which ones were picked up at the supply house, and which ones were leftover from last week's job. The work order goes in marked-up at "materials = $185" with no detail.

End of week: The shop's parts spending is $1,800 higher than expected. Nobody knows why. The trucks have an extra two boxes of fittings nobody can account for. The invoice mark-up on parts is somewhere between "hopefully right" and "definitely wrong."

Fix all of this with six steps.

The foundation of truck inventory is a documented par list — the minimum stock level for every part that should be on every service truck, every day. Without a par list, you are guessing about what to restock and the trucks drift over time.

A typical residential service truck par list has 80-150 line items grouped into sections:

Pipe and fittings: 1/2", 3/4", and 1" copper, PEX, CPVC, and PVC in straight pieces, elbows, tees, couplings, reducers, unions, and end caps. Minimum quantities: 10-30 of each common fitting; 4-8 of each less common.

Shutoff valves: 1/2" and 3/4" ball valves, gate valves, angle stops, dishwasher and ice maker stops, supply stops in compression and threaded. Minimums: 6-12 of each.

Supply lines: 12", 16", 20", 24" stainless steel braided in 3/8" and 1/2" connections. Faucet supply lines, toilet supply lines, dishwasher supply lines. Minimums: 4-8 of each length and connection.

Toilet parts: Wax rings (regular and extra-thick), closet bolts, fill valves, flappers (Korky and Fluidmaster compatible), toilet flanges, supply lines. Minimums: 6-12 of each.

Faucet parts: Common cartridges for Moen, Delta, Kohler, Pfister, Price Pfister. Minimums: 2-3 of each common cartridge.

Water heater parts: T&P valves, anode rods, dip tubes, heating elements (4500W and 5500W), thermostats, drain valves, gas control valves. Minimums: 1-3 of each.

Drain parts: Drain assemblies, p-traps in 1.25" and 1.5", trap arms, slip joint nuts and washers, tubular fittings. Minimums: 3-6 of each.

Consumables: Pipe dope, Teflon tape, plumber's putty, silicone, primer and cement (PVC, CPVC, ABS), flux, solder, sandpaper, abrasive pads, rags. Minimums: 2-4 of each.

The par list lives in the inventory system, not on a paper checklist taped to the shop wall. Each truck is treated as its own location with its own quantities-on-hand. When a part is used on a job, the count drops. When the count hits the minimum, a restock alert fires.

The gotcha: do not blanket-set a high par across all parts. Truck weight matters, and stocking 40 of a part you use twice a year is just as wasteful as running out. Look at your last 12 months of parts usage and set the par to roughly 2-3 weeks of typical usage for each item.

The second leak is invoice markup. Plumbing shops survive on parts margin almost as much as labor margin, and most shops are leaving money on the table here.

Standard parts markup ranges in 2026:

Common consumables and small fittings (under $5 cost): 80-120% markup. A 1/2" PEX coupling that costs the shop $0.80 sells on the invoice for $1.50-$1.80. A wax ring that costs $2.50 sells for $5-$6.

Mid-range parts ($5-$50 cost): 60-100% markup. A faucet cartridge that costs $18 sells for $32-$36. A T&P valve that costs $14 sells for $25-$28.

Larger parts ($50-$300 cost): 40-70% markup. A water heater anode rod that costs $35 sells for $55-$60. A circulator pump that costs $180 sells for $260-$300.

Major equipment ($300+ cost): 25-50% markup. A 50-gallon water heater that costs the shop $650 sells for $850-$950 installed (with labor and other fittings billed separately). A high-end faucet that costs $200 sells for $280-$300.

The markup compensates for: parts handling time, truck inventory carrying cost, parts loss and shrinkage (the 8-12% lost-on-truck rate), warranty claims that come back to the shop, and the cost of capital tied up in inventory. Shops that mark up at "matrix cost + 25%" universally lose money on small parts and are subsidizing those losses with labor margin.

The specific tactical setup: the inventory system carries a cost field and a markup field for every part. The markup is set per category (consumables, fittings, valves, equipment, etc.) and overridable per part if needed. When a tech adds a part to a work order, the system auto-applies the markup. The tech does not see the markup math — they see the customer-facing price. The owner audits the markup table once a quarter against current supply-house cost to make sure the markups are still right as cost of goods has shifted.

The gotcha: never let techs hand-edit prices on invoices in the field. Once that door is open, the markup system becomes negotiable and customers eventually compare prices across visits. Lock the prices to the system; if a discount is warranted, the discount goes through the owner or office manager, not the tech.

The third step is closing the loop on the truck. Every part used on a job has to be logged on the work order — not as a lump-sum "materials = $185" line, but as the actual line items: 6 x 1/2" copper couplings, 2 x 3/4" ball valves, 1 x T&P valve, 6 ft of 3/4" copper pipe.

Three ways to do this in the field:

Tap-to-add from a parts catalog. The mobile app shows the truck's stock with the most-used parts at the top. Tech taps a part, taps a quantity, repeats for each. Takes about 30-45 seconds for a typical job. Works for 90% of shops.

Barcode scanning. Each part bin on the truck has a barcode. Tech scans the barcode and enters the quantity used. Faster than tapping for shops with 100+ parts on the truck. Requires the upfront work of barcoding bins, which is a 4-6 hour project for one truck.

RFID tagging (newer). RFID tags on bins and an RFID reader in the truck count parts automatically as they move in and out. Higher upfront cost ($800-$2,000 per truck) but zero per-job logging time. Worth it for high-volume commercial shops; overkill for residential.

Whichever method you pick, the rule is the same: no work order closes until the parts list is complete. The mobile app should block the close-out step if the materials section is empty on a job that obviously used materials.

When the tech closes the work order, the inventory system does two things: deducts the used parts from the truck's stock, and adds the parts to the customer-facing invoice with the marked-up price. No double entry, no end-of-week reconciliation.

The gotcha: the parts catalog has to be ruthlessly maintained. SKUs that go obsolete need to be deactivated. New SKUs need to be added the day they hit the truck. Catalog drift is the #1 reason field tech parts logging breaks down — if the part isn't in the catalog, the tech writes "misc" and the system stops working.

Even with great in-app logging, trucks drift. Parts get borrowed between trucks, customers occasionally walk off with stuff, fittings fall behind a toolbox and stay there for months. The fix is a weekly truck audit.

The audit takes about 30-45 minutes per truck and runs every Friday afternoon or Saturday morning:

Step 1. Pull up the system's current truck stock count for each part. Print or display the par list with quantities-on-hand.

Step 2. Physically count each section of the truck — pipe and fittings, valves, supply lines, toilet parts, faucet parts, water heater parts, drain parts, consumables. Compare actual count to system count.

Step 3. For any discrepancy of more than 2 units, investigate. Most discrepancies are explained by a job in the last week that wasn't fully logged. The tech should be able to walk back through the week's work orders and fill in the missing parts. Sometimes the discrepancy is a part that was loaned to another tech — log that too.

Step 4. Adjust the system count to match physical count. The audit replaces any drift accumulated over the week.

Step 5. Restock from the shop's main inventory to bring the truck back to par. The restock list comes from the par minus current count. The shop's main inventory drops by the restocked amount.

The weekly audit serves three purposes: catches logging gaps before they become large, keeps the trucks at par so techs don't run out mid-job, and surfaces the patterns of which trucks lose more parts (which usually points to a tech who needs a refresher on logging discipline).

The gotcha: do not skip the audit when things are busy. The week you skip it is the week the discrepancies get large enough to be expensive. Block 30-45 minutes per truck on the calendar every week and treat it as non-negotiable.

The fifth step is keeping the shop's main inventory stocked so the weekly truck restocks don't run dry. This is where automation pays off — most shops are still walking the aisles of the supply house with a sticky note.

The automation: every part in the inventory system has a reorder point and a reorder quantity. When the shop's main stock of any part drops below the reorder point, an alert fires. The alert can be a single weekly digest (every Monday morning, here are 23 parts that need to be reordered) or a real-time email per part (rarely worth it — too noisy).

The weekly digest gets reviewed by the office manager or owner. The reorder quantity is the default but can be adjusted based on upcoming jobs (a scheduled water heater install means ordering an extra 4 anode rods this week). The order goes to the supply house — Ferguson, Hajoca, Winsupply, or whoever the shop's primary supplier is — either through their online portal, a faxed PO, or an EDI integration if the shop is large enough.

When the parts arrive, they get checked in against the PO and the quantities are added back to the shop's main inventory. Trucks restock from the shop the next morning.

The gotcha: do not let one supply house become a single point of failure. Stock the most critical 30-40 parts at two suppliers if possible, so a backorder at one place doesn't shut down jobs. The newer parts inventory tools include multi-supplier sourcing as a feature.

The final piece is measurement. A clean inventory system gives you a number for shrinkage — the percentage of parts purchased that don't show up on either a customer invoice or in the current truck/shop stock.

The formula is simple: (parts purchased over a 90-day window) minus (parts billed on customer invoices) minus (current parts on hand at start of next quarter) divided by (parts purchased) equals shrinkage rate.

A shop with no system typically runs 8-12% shrinkage. A shop with a working inventory system, weekly audits, and parts logging discipline can get this to 1-2%. The 6-10 percentage-point swing on a $80,000 annual parts spend is $4,800-$8,000 a year recovered — straight to the bottom line.

Review shrinkage quarterly. If it's drifting above 3-4%, look at: which parts are leaking (small consumables typically lead), which trucks are over-leaking (audit those weekly without fail), and whether the parts catalog has gaps that are forcing techs to write "misc" on work orders.

The gotcha: do not chase 0% shrinkage. There will always be small losses — wax rings used on warranty callbacks that don't get billed, fittings that genuinely fall behind a wall, the occasional part stolen from a job site. Aim for under 2% and stop optimizing. The marginal effort to chase from 2% to 0.5% costs more in time than it saves.

Deelo's inventory system treats every truck as its own location with par levels, current stock, and reorder points. The Field Service mobile app shows the tech's truck-specific catalog with the most-used parts pinned to the top. Tap-to-add or barcode scanning logs parts to the work order, deducts from truck stock, and adds the marked-up line item to the invoice — all in a single action.

Markup is configured per category in the inventory settings, so consumables get the 80-120% bump, mid-range parts get 60-100%, and major equipment gets 25-50%. Techs never see or edit the markup; they see the customer-facing price.

The weekly truck audit runs as a guided checklist in the app — section by section, the manager taps each part, enters the physical count, and the system flags any discrepancy over the threshold. Restock orders auto-generate to bring trucks back to par.

The shop's main inventory feeds into a weekly reorder digest with the parts to source from each supply house. The shrinkage report runs quarterly and shows the percentage by truck, category, and trend over the last four quarters.

For a 4-truck plumbing shop with $80,000 in annual parts spend, getting shrinkage from 10% down to under 2% recovers $6,000-$8,000 a year. At $19/seat/month for the full Deelo platform, the inventory system pays for itself in the first six weeks.