ATC Pacific Under Sink Water Heater, 5L, 10L or 14L

The ATC Pacific is a compact under sink water heater, also called an undersink water heater, that supplies hot water to one or more basins through ordinary taps. It comes in three sizes: 5L at 2000W, 10L at 2000W and 14L at 2500W. It is an unvented heater that connects directly to the mains water supply, with a maximum pressure of 8 bar and a minimum operating pressure of 1 bar, so it is not suitable for gravity fed systems. It runs on 220V to 240V and comes pre-wired with 1.5mm² cable, 2 core and earth, for connection to a 13A double pole switched spur. From 10°C to 65°C, the 5L heats in about 11 minutes, the 10L in about 19 minutes and the 14L in about 22 minutes. It hangs on the wall bracket or stands on the adhesive rubber feet, and both are included. ATC lists it for offices, canteens, mobile homes, apartments and workshops.

Key Features

• Three sizes: 5L, 10L and 14L, supplying from 1 basin up to 4 basins as a guide.
• No special taps: it works without the need for special taps.
• External adjustable thermostat with an economy setting. The range is 30°C to 80°C on the 5L and 35°C to 75°C on the 10L and 14L.
• Heating indicator light: on while the element is heating, off once the water reaches the set temperature.
• On and off switch on the 10L and 14L. The 5L has no external switch.
• Two ways to fit it: on the wall with the bracket, or standing on its base with the rubber feet.
• Quick recovery element: 2000W on the 5L and 10L, 2500W on the 14L.
• Tank protection: porcelain enamel lining and a magnesium anode rod to resist corrosion.
• Polyurethane foam insulation to reduce heat loss.
• Overheat protection: a thermostat plus a resettable thermal cutout that shuts off the element if the water exceeds 93°C.

Specifications

The 14L model carries the code W15-U, but its capacity is 14 litres.

What Is in the Box

• Water heater
• Mounting bracket and a bag of fixings
• 4 adhesive rubber feet
• 6 bar pressure relief valve
• 2 dielectric connectors
• Instruction manual

Installation

ATC says the heater should be installed by a qualified installer. It must be earthed, and a suitably qualified electrician should make the electrical connection, using a double pole switch beside the heater. In a bathroom, the circuit must be protected by a 30mA RCD. Install it close to a drain, so that water from the pressure relief valve can run to waste.

All water connections to the heater must be in copper pipe, with at least 1 metre of copper between the heater and any plastic pipe. The pressure relief valve must never be mounted on the heater itself, and its outlet should point down and be piped to waste. ATC shows three layouts, depending on the inlet water pressure:

• Up to 4.1 bar: allow 2.8m of pipework for the 5L and 10L, or 4.2m for the 14L, for expansion between the cold water inlet and the non return valve.
• Up to 4.1 bar where expansion in the mains is not possible: fit an expansion vessel, ATC Kit-A, which is 2L with a 1/2 inch BSP connection.
• Over 4.1 bar: fit a pressure reducing valve, ATC Kit-B, and the Kit-A expansion vessel. An expansion vessel must be used whenever a pressure reducing valve is fitted.

Kit-A, Kit-B and the Kit-C tun dish are optional ATC accessories and are not included. The non return valve and service valve come from a plumbing merchant.

Maintenance

• Inspect the magnesium anode rod every year and replace it if needed. ATC warns that failing to do this could cause the tank to fail and void the warranty.
• Test the pressure relief valve at least once every six months.
• Leave servicing to a qualified person.

Running Costs

The energy label gives 576 kWh a year on the XXS load profile, for all three sizes. That is roughly €219 a year at 38.04 cent per kWh, the Electric Ireland 24 hour standard rate from 1 July 2026. One full heat from 10°C to 65°C uses about 0.37 kWh on the 5L, 0.63 kWh on the 10L and 0.92 kWh on the 14L, worked out from ATC's heat up times. That is roughly 14 cent, 24 cent and 35 cent. Real costs depend on how much hot water you use and the thermostat setting.

Frequently Asked Questions

Q: Where can I buy an under sink water heater in Ireland?
A: From Shamrock Electrical at shamrockelectrical.ie, with free delivery to every county in the Republic of Ireland from the first euro. You can also order for collection from our shop in Greenogue Business Park, Rathcoole, Co. Dublin, usually ready in 2 to 4 days. Please ring or email first, as most items on the website are not kept in the shop.

Q: What size under sink water heater do I need?
A: It depends on the number of basins. As ATC's guide, the 5L suits 1 to 2 basins, the 10L suits 2 to 3 basins and the 14L suits 3 to 4 basins. These figures are for guidance only, and the right size also depends on hot water demand.

Q: Does it come with a plug or is it hard wired?
A: It is hard wired. It comes pre-wired with 1.5mm² cable, 2 core and earth, and ATC says the cable should connect to a 13A double pole switched spur. A suitably qualified electrician should make the connection, and the heater must be earthed.

Q: Will it work on a gravity fed system?
A: No. ATC states it is not suitable for gravity fed systems. It connects directly to the mains water supply and needs a minimum operating pressure of 1 bar.

Q: Do I need special taps?
A: No. ATC states the Pacific can supply a number of sinks without the need for special taps.

Q: Do I need an expansion vessel?
A: It depends on your water pressure and pipework. Over 4.1 bar, you need a pressure reducing valve and an expansion vessel. Up to 4.1 bar, you need a vessel if you cannot allow 2.8m of pipework for expansion on the 5L or 10L, or 4.2m on the 14L.

Q: How much does it cost to run?
A: Roughly €219 a year, from the 576 kWh on its energy label at 38.04 cent per kWh, the Electric Ireland 24 hour standard rate from 1 July 2026. One full heat from 10°C to 65°C costs roughly 14 cent on the 5L, 24 cent on the 10L and 35 cent on the 14L. Real costs depend on how much hot water you use.

Q: What warranty does it have?
A: A two year limited parts warranty from ATC, as long as the heater is installed, used and maintained as the manual describes. The anode rod needs inspecting every year, because ATC warns that failing to do so could void the warranty. Full terms are at atc.ie.

Every order ships with free delivery from the very first euro, with no minimum spend and no threshold to reach. New customers take 10 percent off a first order. Trade pricing is not shown online, so if you are buying for a job or a contract, call us on 01 401 9907 or email sales@shamrockelectrical.ie for your rate. We are an Irish owned electrical supplier based in Greenogue Business Park, Rathcoole, just off the N7 and well positioned for the M50.