For a plumbing or hydronic heating contractor, a supply chain problem rarely stays a supply chain problem for long.

A backordered circulator, valve, water heater or control can quickly become a scheduling problem. Then it becomes a customer-service problem. If a crew is standing around waiting for material, it becomes a labor-cost problem too.

The disruptions of the past few years have eased in some areas, but that does not mean contractors can go back to assuming everything will be available tomorrow. The better approach is to build a little flexibility into purchasing, inventory and storage before the next shortage hits.

Here are five practical ways to do it.

1. Identify the Parts You Really Cannot Work Without

There is a big difference between keeping useful inventory and simply accumulating material.

Start with the fittings, valves, pumps, repair parts and other items your technicians use repeatedly. Look at service tickets from the past six or twelve months and determine which materials consistently leave the shop or service trucks.

Those are the items where running out can turn a straightforward service call into two trips.

This does not mean filling the warehouse with every possible SKU. Slow-moving material ties up cash and eventually becomes obsolete. CONTRACTOR Magazine has made the same point in its discussion of inventory control: contractors should know what moves, what sits and how much money is tied up in stock.

The goal is not maximum inventory. It is the right inventory.

2. Build a Backup Supplier Before You Need One

The worst time to start looking for another source is when your regular supply house tells you an essential part will not arrive for six weeks.

Maintain relationships with more than one distributor where practical, particularly for high-use or long-lead items. It is also worth knowing which manufacturers have interchangeable or approved alternatives for products you install regularly.

Contractors are already doing this.

In the Associated General Contractors of America's 2025 Construction Outlook, 33% of responding firms said they had turned to alternative suppliers because of supply-chain issues in 2024, while 26% had specified alternative materials or products. Another 44% accelerated purchases after winning contracts.

You do not need three suppliers for every fitting in the truck. But having a Plan B for critical equipment can keep one delayed order from stopping an entire job.

3. Order Long-Lead Equipment Earlier

A contractor's purchasing schedule should not always follow the installation schedule.

When equipment has a history of extended lead times, identify it during estimating and procurement instead of waiting until crews are ready to install it.

Boilers, water heaters, pumps, specialty valves, controls and project-specific equipment deserve particular attention. As soon as a project is awarded, confirm current availability and expected delivery dates.

For larger projects, that may mean purchasing certain items weeks or months before they are actually needed.

The important part is communication. The estimator, project manager, purchasing staff and field supervisor should all know which materials represent schedule risk. A simple long-lead list reviewed regularly can prevent a surprising number of problems.

4. Have a Plan for Material That Arrives Early

Buying earlier solves one problem but can create another: where do you put everything?

The shop may have enough room during normal operations but become crowded when material for two or three upcoming projects arrives at the same time.

Before increasing inventory, decide where it will go and how it will be tracked.

Depending on the operation, that could mean dedicated warehouse shelving, a secured area at the jobsite or temporary on-site storage. Portable shipping containers are another option when contractors need short-term capacity without adding permanent warehouse space. If that route is used, organization matters; this practical guide to shipping container storage and organization covers shelving, zoning frequently used inventory, labeling and keeping material off the floor.

Whatever storage method you choose, establish locations for each project and label material clearly. Buying ahead does little good if a technician cannot find the part when it is needed.

5. Decide Which Jobs Get Scarce Material First

When supply tightens, not every job has the same priority.

Emergency service, scheduled replacements and construction projects with firm deadlines may compete for the same equipment. Waiting until the material is already scarce to decide who gets it puts dispatchers and project managers in a difficult position.

Establish some basic rules in advance.

Which items are reserved for committed projects? How much service stock should remain untouched? Who can authorize taking material allocated to another job?

For a small contractor, this does not require sophisticated software. A shared inventory sheet and clear responsibility may be enough. What matters is that somebody knows what is in stock, where it is and which job it belongs to.

A Little Flexibility Goes a Long Way

No contractor can control a factory shutdown, transportation delay or sudden shortage.

What a contractor can control is how exposed the company is when one happens.

Keeping sensible quantities of critical parts, maintaining backup suppliers, identifying long-lead equipment early and having flexible storage available will not eliminate supply-chain problems. But those steps can keep a delayed shipment from becoming a delayed project—and keep technicians working instead of waiting.