Preventive maintenance: how to draw up a maintenance plan for your customers’ installations

What does preventive maintenance mean?

Preventive maintenance is maintenance you plan before something breaks. At a set moment, the technician cleans, measures, adjusts and replaces wearing parts. That way, the installation keeps working as intended, and you see wear before it becomes a breakdown.

Corrective maintenance happens after the breakdown: the customer calls, the technician looks for the cause and repairs it. Every service company does both. The question is what share of the work you plan yourself.

The difference between preventive and corrective maintenance

Preventive maintenance does not prevent every breakdown. A unit can fail between two visits, and then corrective work is still needed.

Time-based or condition-based maintenance

• Time-based maintenance follows a fixed interval: every year, every six months or after a number of operating hours. It is easy to plan and to agree in a contract. But a unit that runs little gets the same maintenance as a unit that works day and night.
• Condition-based maintenance follows what you measure or find: a filter with too high a pressure drop, a water softener whose treated water is getting harder, a boiler with a recurring error code.

In practice, you combine the two. At the fixed visit, the technician measures and records, and what they find decides whether an extra intervention is needed. Predictive maintenance, which tries to predict a breakdown from continuous measurement data, is a third form and is outside the scope of this article.

Drawing up a maintenance plan

A maintenance plan says, for each installation, what is done, how often, by whom and when. How you record this with the customer in a contract is covered in tracking maintenance contracts. Here, it is about the plan itself.

1. Make the inventory

For each installation, note the customer, the site, the type, the make and model, the serial number, the installation date, the last maintenance and the access. Add one piece of information that is often missing: what does a breakdown cost the customer? A boiler in a residential care home calls for a different plan from the same boiler in a holiday home. Whatever is missing, the technician fills in at the next visit, with a photo of the rating plate.

2. Set the frequency per type

• The manufacturer’s manual is the starting point. Also check whether the warranty conditions require maintenance.
• The rules of the region where the installation is. In Flanders, a central heating appliance on gas from 20 kW must be serviced every two years, and an appliance on heating oil from 20 kW every year, each time by an accredited technician (vlaanderen.be, consulted on 30 October 2026). In Brussels, the periodic EPB inspection of a gas boiler is required every two years, and that of a boiler on heating oil or solid fuel every year, by an accredited EPB boiler technician (environnement.brussels, page of 19 January 2025, consulted on 30 October 2026). In Wallonia, the periodic inspection takes place every year for an oil-fired boiler and every three years for a small domestic gas boiler, by an accredited technician (energie.wallonie.be, consulted on 30 October 2026). Check what applies to each type and, if in doubt, ask the region or your legal adviser.
• Use. An installation that runs intensively, stands in dust or treats hard water gets more visits. Never go below what the manufacturer or the rules require.

3. Record what happens at each visit

Make a fixed list per type: what the technician cleans, replaces, checks and measures. Have them record the readings every time, because a value that drifts from visit to visit only shows up if it was recorded. How to build such a list is covered in writing a work instruction.

4. Decide who does it

Which technicians have the certification or the training for this type? Who is the regular technician for an area or a customer, and who takes over during their leave? With a second technician who knows the type, the plan does not stall during an absence.

5. Plan the year ahead

• Choose the season. A boiler is best serviced before the heating season, an air conditioner before the summer.
• Group by area. Put visits in the same street or the same building on the same day.
• Reserve capacity. Decide per week how many hours go to planned maintenance, and keep room free for breakdowns. More on this in scheduling technicians.

An example of a maintenance plan

An example to adapt, not a standard: the manufacturer’s manual and the regional rules always take precedence.

How do you know whether the plan works?

• Visits on time. Which visits are overdue? If that list grows every month, the plan asks more than your team can handle.
• Breakdowns between two visits. If an installation fails shortly after a visit, look at what was measured then. If it happens often with the same type, adjust the frequency or the list.
• Repeated breakdowns with the same cause. They point to something the visit does not cover.
• Installations without a plan. Every unit in the inventory has a next maintenance date, or a reason why not.
• Planned versus unplanned work. Track each month how many interventions were maintenance and how many were breakdowns. More figures in field service KPIs.

An example: a water treatment company sets up its plan

A company that installs water softeners and filters has worked with a list per technician for years. When switching to a maintenance plan, the owner starts with the inventory: which units did we install or maintain, for whom, and when was the last visit? Some of the units turn out to have no next visit anywhere.

Homes get one visit a year, hospitality businesses with high consumption two visits a year. The list for each visit is the same everywhere: measure the hardness before and after, check the salt consumption and the settings, take a photo. After a year, the recorded values show that, at a few large families, the hardness after the softener is higher at every visit. From now on, those customers get two visits a year.

How it works in Digitalnatie Service Suite

• The inventory: in the installations register, you record each unit with, among other things, its make and model, serial number, installation date and criticality, always with a customer and a site. A column shows the next maintenance: on schedule, due soon, overdue or not scheduled.
• The plan: in the maintenance contracts screen, you create a contract for one installation or a whole site, with a frequency from monthly to yearly or a custom number of days, an optional technician and a visit template with the instructions and the duration of each visit. The form shows the next six visit dates.
• The visits: once a day, for each active contract whose next visit has been reached, Service Suite creates a preventive maintenance intervention, which you then put in the schedule. An extra visit, for example after a measurement, is created from the contract or from an installation in the register.
• Planning ahead: in the schedule, fixed routes link a technician, weekdays, a maximum per day and sites. Interventions at those sites get the route’s technician.
• Follow-up: the contracts screen has tabs for overdue visits and for visits within the next 30 days. The installation file shows its maintenance history and its breakdowns, the health screen the most frequent and repeated breakdowns, and the reports split the interventions by type: contract maintenance, breakdown and other.

Good to know:

• The health score out of 100 deducts points according to fixed rules, for the recorded breakdowns, downtime, overdue maintenance, costs and repeated breakdowns. It is not a forecast: it describes what has happened. No breakdown prediction is calculated.
• A completed intervention does not automatically move the installation’s next maintenance date. A unit that has been serviced can therefore remain overdue.
• Without a site, Service Suite does not create any visits, and missed visits are not created afterwards. The automatic creation cannot be started manually: for a visit that has to happen straight away, schedule it from the contract.

More about maintenance contracts in Service Suite. What goes into the unit’s file after each visit is covered in the service history per installation.

Frequently asked questions

What does preventive maintenance mean?

Preventive maintenance is maintenance planned before there is a breakdown: cleaning, measuring, adjusting and replacing wearing parts at a set moment. That way, an installation keeps working as intended, and wear is noticed before it becomes a breakdown.

What is the difference between preventive and corrective maintenance?

You plan preventive maintenance in advance, on a date or after a finding. Corrective maintenance follows a breakdown or a defect, and is done as fast as the priority requires. A service company always does both; the maintenance plan determines what share of the work you plan in advance.

What is the difference between time-based and condition-based maintenance?

Time-based maintenance follows a fixed interval, such as every year or after a number of operating hours. Condition-based maintenance follows a measurement or a finding, such as too high a pressure drop across a filter. In practice, the technician measures at the fixed visit, and the measurement decides whether more is needed.

How do you draw up a maintenance plan?

Start with the inventory of the installations you maintain. Set the frequency per type, based on the manufacturer’s manual and the regional rules. Record what happens at each visit and who does it, plan the year ahead and check that the visits happen on time.

Does Service Suite predict when an installation will break down?

No. An installation’s health score describes the past, such as breakdowns, downtime and overdue maintenance. No breakdown prediction is calculated.