Tankless Water Heaters near you

An appliance with no store can only heat what passes through it. Its useful output is therefore a combination of two things: how many litres a minute it can pass, and how far it can lift the temperature of that water on the way. Open a second tap and the same heat is shared between two outlets, which is why a household running a shower and a kitchen tap at once notices an instantaneous appliance in a way that a household with a cylinder does not.

The incoming water is the part people forget. Mains water arriving at a British house is markedly colder in February than in August, so the same appliance has to work harder in winter to reach the same temperature, and it does that by passing less water. A shower that was acceptable in summer and disappointing in winter is usually not broken; it is being asked for a bigger temperature rise at the same flow.

The incoming main sets the ceiling too. If the supply pipe cannot deliver a decent flow into the house, no instantaneous appliance will deliver a decent flow out of it, which is why the measurement at the stopcock belongs at the survey stage rather than after the appliance is on the wall.

Gas first, because it is not negotiable. The Gas Safety (Installation and Use) Regulations 1998 restrict work on gas fittings to competent people within an HSE-approved class of persons, and every registered engineer carries an ID card recording which appliances they are qualified to work on. HSE also states plainly that it is illegal for anyone to use a gas appliance if they suspect it is unsafe, and that an appliance suspected of being unsafe should be turned off and left alone until a Gas Safe registered engineer has checked it. HSE runs a free gas safety advice line and lists ways to confirm an engineer's registration before work starts.

The water fittings rules treat instantaneous heaters differently from cylinders, and this is the point most often misunderstood. Schedule 2 to the Water Supply (Water Fittings) Regulations 1999 imposes its vent pipe, temperature control, temperature relief and combined temperature and pressure relief requirements on every unvented water heater, but expressly excludes an instantaneous water heater with a capacity not greater than 15 litres. Approved Document G agrees, saying water heaters with a capacity of 15 litres or less that have appropriate safety devices for temperature and pressure will generally satisfy Requirement G3(3). A combi is not an unvented cylinder and does not bring the unvented cylinder regime with it.

Electrical work is its own trade. Approved Document G expects electric instantaneous water heaters to comply with the relevant British and European standard for household appliances, and in England electrical work in dwellings sits under Part P of the Building Regulations, so an electric shower or an over-sink heater usually needs an electrician as well as a plumber. Scotland and Northern Ireland apply their own building standards and their own water fittings rules, the Northern Irish ones made in 2009.

Approved Document L is explicit about what should happen before a new heating appliance goes in: all central heating and primary hot water circuits should be thoroughly cleaned and flushed out, a suitable chemical inhibitor should be added to the primary heating circuit to protect against scale and corrosion, and in hard water areas suitable measures should be taken to treat the feed water to water heaters and the hot water circuit of combination boilers to reduce limescale accumulation. Debris from old pipework and scale from hard water are what destroy the narrow passages an instantaneous appliance depends on.

The paperwork is part of the job rather than an afterthought. Approved Document L points to a commissioning checklist as the way of showing that the heating and hot water system and its heat source were commissioned satisfactorily, and most manufacturers' warranties depend on that record being completed and on the appliance being serviced at the stated interval by somebody holding the right registration.

Fitting a new gas combi in a house that already has one is not simply a like-for-like swap in regulatory terms. Approved Document L says that if a gas-fired combination boiler is installed in an existing dwelling, at least one of the following energy efficiency measures, appropriate to the system, should be installed: flue gas heat recovery, weather compensation, load compensation, or a smart thermostat with automation and optimisation. Ask which one is included and how it will be commissioned, because it is a requirement of the installation rather than an upsell.

Whether to repair or replace usually turns on what has failed and on what the household needs next. A failed sensor or diverter valve on an otherwise sound appliance is worth fixing; a heat exchanger scaled solid in a hard water area, or a model the manufacturer no longer supports, starts to argue for replacement. If the household has grown out of one hot flow at a time, the honest answer may be a cylinder rather than a better instantaneous appliance.

There is no grant for putting in another gas combi. The Boiler Upgrade Scheme, which is open to people in England and Wales, gives grants towards replacing fossil fuel heating systems — oil, gas, electric or LPG — with a heat pump or a biomass boiler, so it rewards moving away from an instantaneous gas appliance rather than renewing one.

The devolved picture differs. GOV.UK directs householders in Scotland to separate interest-free loan and grant support for making a home more energy efficient, and notes that the Boiler Replacement Scheme in Northern Ireland has closed, pointing readers to local energy saving grants instead. Check what is open where you live before assuming a quotation can be reduced by a grant.

LokalMatch covers the first step only: you set out the appliance you have or want, what the household needs from it and your postcode once, and installers working nearby contact you, having paid for the request. LokalMatch does not install or repair anything, has no say in what any installer charges, and does not vet, rank or recommend the businesses that respond, so ask each one which registrations they hold for your appliance and what their quotation includes.