What a Heat Pump Plumber Does
A heat pump plumber in Ireland handles the pipework, commissioning and hot-water cylinder work that connects a heat pump to your home's heating system. This is a distinct role from the HVAC installer who supplies and fits the heat pump unit itself. The two trades often work the same job at different stages, so knowing what each one does tells you who to hire and when.
Pipework installation
The plumber connects the heat pump to your existing wet heating system, whether that is a radiator circuit or underfloor heating. In most retrofits the existing pipework can be reused with modifications. Where radiators are too small for the lower flow temperatures a heat pump produces, the plumber replaces them with larger panels or adds radiators to the circuit.
Hot-water cylinder work
Most existing cylinders are not compatible with heat pumps. The plumber assesses your current cylinder and, in most cases, replaces it with a heat-pump-specific model with a larger coil designed for low-temperature heat transfer. This is one of the significant costs in any retrofit.
Commissioning
Commissioning is the final stage: the plumber pressure tests the pipework, balances the circuit, sets the flow temperature, configures the controls and completes the documentation. Without a properly commissioned system a heat pump runs inefficiently and may not meet your SEAI or BER requirements.
Commissioning: The Plumber's Checklist
Commissioning is not a quick sign-off. A thorough visit typically takes four to six hours and covers every element of the heat pump's interaction with your plumbing. Here is what an RGI plumber works through.
- Pressure testing all pipework. The heating circuit is tested before any water goes in. A system that holds pressure at 1.5 times working pressure is ready to fill.
- Balancing radiators and underfloor circuits. Each zone is balanced so heat is even across the house, which matters more at a heat pump's lower flow temperatures.
- Setting the flow temperature. Heat pumps are most efficient at 35 to 45 degrees. The plumber sets this and confirms the radiators can heat the home at that temperature.
- Commissioning the cylinder. The new cylinder is filled and brought up to temperature, the immersion backup is tested and the legionella cycle is configured.
- Configuring controls. Time schedules, weather compensation and any smart thermostat are set so the heat pump modulates output rather than running flat out.
- Commissioning record and handover. The plumber completes the record required for your SEAI grant and BER cert, and gives you a copy to keep.
The Hot-Water Cylinder: What Changes
Most homes switching to a heat pump need a new cylinder. The standard vented copper cylinder in most Irish homes is designed for the high flow temperatures of a gas or oil boiler. A heat pump runs cooler, so the coil inside the cylinder needs to be much larger to transfer the same heat.
What type of cylinder does a heat pump need?
A heat pump cylinder is an unvented pressurised unit with a large lower coil, typically 2.5 to 3 metres long, sized for 35 to 45 degree flow temperatures. It is larger than a standard cylinder, usually 200 to 300 litres, with an immersion heater as backup for cold spells.
Twin-coil cylinders for solar
Many plumbers recommend a twin-coil cylinder. The second coil can connect to a solar thermal panel later, so you can add solar water heating without replacing the cylinder again. A small upfront cost for a common long-term win.
Cylinder costs
Supply and installation of a heat pump cylinder typically costs €1,500 to €2,500, depending on capacity and whether the location changes. This is separate from the heat pump unit. See our hot water cylinder guide for more.
Pipework and Your Existing Radiators
A common question is whether your existing radiators can stay. The answer depends on their size relative to the rooms they heat and the flow temperature the heat pump runs at.
Why flow temperature matters
A gas boiler heats water to 70 or 80 degrees; a heat pump is most efficient at 35 to 45. At a lower temperature a radiator gives out less heat, so one that was fine on a boiler may be too small at heat pump temperatures.
Radiator sizing
Your plumber calculates the heat loss per room and checks each radiator's output at the target temperature. Options are larger panels, an extra radiator, or a slightly higher flow temperature in that zone. In most Irish semis built after 1980, the majority of radiators can be kept with selective upgrades.
Underfloor heating
If you have underfloor heating, a heat pump is an ideal match, as it runs at 30 to 40 degrees, well within a heat pump's efficient range. See our underfloor heating guide.
Is Your Home Ready? Three Checks
A heat pump performs best in a well-prepared home. Getting three things in order before the trades arrive saves money, improves efficiency and protects your SEAI grant eligibility.
Insulation
A heat pump only reaches its designed efficiency in a well-insulated home, and SEAI requires a BER assessment before approving the grant. Do insulation before or alongside the heat pump. Find a SEAI-registered insulation contractor at wallinsulationireland.ie.
Gutters and roof drainage
Blocked gutters and roof leaks introduce damp, which undermines insulation and raises heat loss. Address roof or drainage issues first. Find a rated roofer at roofersinireland.ie.
Electrical supply
A heat pump needs a dedicated 32A circuit wired by a RECI-registered electrician before the plumber commissions the unit. The plumber and electrician coordinate the commissioning date between them.
RGI Registration and Gas Disconnection
If your current system is a gas boiler, it must be safely decommissioned and disconnected before the heat pump is commissioned. This work must be carried out by an RGI (Registered Gas Installer) engineer, a legal requirement under the Energy (Miscellaneous Provisions) Act 2006. An unregistered person cannot legally disconnect a gas appliance, and a property sale or insurance claim may be affected if this was done without registration.
How to verify an RGI number
The Register of Gas Installers of Ireland publishes a public searchable register at rgi.ie. Enter the engineer's name or number to confirm current status, and always verify before any gas work begins.
- Gas disconnection must be done by a current RGI registrant
- Ask to see the registration card before work starts
- The engineer must issue a gas safety certificate on completion
- SEAI grant paperwork requires confirmation of RGI registration
Installer vs Plumber: Who Does What
A heat pump installation in Ireland involves two separate tradespeople, each responsible for a distinct part of the job. Knowing who does what helps you plan the timeline and get the right quotes.
| HVAC installer | RGI plumber |
|---|---|
| Selects and supplies the heat pump unit | Connects the heat pump to the wet system |
| Handles the SEAI grant application | Replaces and commissions the cylinder |
| Mounts the outdoor unit and runs refrigerant lines | Balances radiators and underfloor circuits |
| Responsible for the BER assessment | Sets flow temperatures and controls |
Many heat pump companies include a plumber in their team, so one contractor covers both. If you manage the trades separately, agree the commissioning date in advance, as the plumber cannot begin until the unit is in place and the refrigerant circuit is complete. To find a registered installer, see heat pump installers at hvacinireland.ie.
Heat Pump Plumbing Costs in 2026
The costs below cover the plumber's work only: pipework, commissioning and cylinder replacement. They do not include the heat pump unit or its installation, which the HVAC installer manages. All figures are for the Republic of Ireland in 2026 and include labour and VAT. Always get at least two quotes.
| Job | Typical cost | Notes |
|---|---|---|
| Heat pump cylinder, supply and fit | €1,500–2,500 | 200 to 300L unvented |
| Pipework and circuit modifications | €600–1,200 | Varies with complexity |
| Radiator upgrades (per radiator) | €200–450 | Most homes need 2 to 4 |
| Full system commissioning | €400–800 | Controls and documentation |
| Gas boiler disconnection (RGI) | €150–350 | When decommissioning gas |
| Total plumbing, with cylinder | €2,500–4,500 | Cylinder plus all plumbing |
For a full overview of plumbing prices, see our plumbing costs guide.
Key takeaways
- A heat pump plumber handles the pipework, commissioning and cylinder work, a distinct role from the HVAC installer who supplies and fits the unit.
- Most existing cylinders are not compatible, so the plumber usually fits a heat-pump-specific cylinder with a larger low-temperature coil.
- Commissioning takes four to six hours: pressure testing, balancing, setting flow temperature, configuring controls and completing the documentation.
- A gas boiler must be decommissioned by a registered RGI engineer before the heat pump is commissioned.
- Plumbing work including the cylinder typically totals €2,500 to €4,500 in 2026, separate from the heat pump unit itself.
