The number to watch
Stock accuracy on your top fifty fittings. A pipe shop carries thousands of lines, but fifty of them are most of the turnover, and those are the ones where a stockout costs you a sale and often the customer. Set minimum levels on those fifty and leave the rest to sell down naturally. Reviewing that short list twice a year against the movement report is twenty minutes that prevents most of the counter disappointments in this trade.
Size and class are the item, not a note
A 1-inch and a 1.25-inch elbow are different products, and so are Class 2 and Class 4 pipe of the same diameter. A shop that enters these as one item can never trust its stock and will regularly bill the wrong rate. Each size and class as its own item, with a code you can search or scan, is the difference between a stock figure that means something and a list that does not.
Length or metre, and cut pipe
Pipe comes in standard lengths and is often sold cut. Holding the unit and the conversion on the item lets you bill either way from the same stock, and the offcut is accounted for rather than vanishing. For a shop with thousands of small fittings alongside the pipe, a barcode on the fast lines makes the counter considerably quicker than searching by name.
Plumber credit against jobs
Your regular buyer is a plumber or contractor drawing material for a job he will invoice later, so the credit runs for weeks and the amounts are small but numerous. What that needs is a party ledger that keeps up without effort, a credit limit so a job that stalls does not keep drawing, and a monthly statement so the account is settled rather than accumulated. Sending that statement unprompted is the habit that keeps these accounts clean.