What to ask when reading a domestic hot water proposal

Afazeres Curiosos · published on 5 November 2026

What the proposal covers

The first step is to see where each proposal begins and ends. Two proposals compare well only when they cover the same set of works, and these questions help to align them.

• Does the proposal include production, storage, the distribution network and the hot water return (recirculation), where there is one?
• Does it include what connects to the system, such as energy supply, water supply, drains, electrical panels and controls?
• Which ancillary works are included, such as openings, reinstating finishes and access?
• Does it include removing the existing system and disposing of the waste?
• What is left to other disciplines or to the owner, and how does that show in the price?

The starting assumptions

Behind any solution are assumptions about the building and those who use it. The owner knows how the building is really used and can help to confirm this data. Each proposal should make clear where it comes from.

• What use of the building was considered: number of occupants, outlets and hours?
• Did this information come from measurements, bills, a site visit or an estimate?
• Was any future change in occupancy or use taken into account?
• Which parts of the existing system were seen, and what condition are they in?
• Is there a reference design? Does the proposal follow it or suggest changes?

Energy, space and connection to the building

A domestic hot water (DHW) system stays in the building for many years. It is worth clarifying with the proposer how the solution fits with what is already there.

• Which energy source is planned, and does the building have it at the capacity needed?
• Does the equipment fit in the available space, and can it get there through the building's access routes?
• Can the location take the expected weight, with drainage, ventilation and noise dealt with?
• How is supply maintained during the works, and which water shutdowns are planned?
• Does the solution depend on another system or part of the building, such as the roof or the heating?

Testing, handover and maintenance

Decree-Law No. 101-D/2020 counts domestic hot water among a building's technical systems (Article 3(x)). In buildings it covers, installations and replacements are carried out by technicians qualified for the purpose (Article 10(2)), and the system's scope is identified and its energy performance assessed and documented (Article 11(1) and (2)). The proposal can state who handles these items.

• Which tests and adjustments are included, and how are they recorded?
• Which documents will be delivered: as-built drawings, data sheets and manuals?
• Who will be trained to operate the system?
• What maintenance does the system need, and with what access?
• What are the warranty terms and the completion period?

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