Buyer’s checklist, 29 September 2026
Boiling water tap problems, and what to check before you order
For homeowners planning a kitchen, and for the fitters and showrooms who get the call when it goes wrong.
The short answer
The same handful of problems come up again and again when owners of boiling water taps write about them in public: not enough room under the sink, a filter that is harder to change or more expensive to keep than expected, limescale in hard-water areas, a safety part or seal that wears out and a support route that stops when the warranty does, and poor flow from airlocks or low mains pressure. Almost none of them is a surprise once the tap is fitted, and each can be checked in writing before you order. This page takes them one at a time: what owners report, what to ask, and where our own figures stand, including the figures we do not yet have.
How this was put together: we read what people write in public, in owner forums, an installation guide and consumer feedback pages, in September 2026. It is a reading, not a survey, so no percentages are implied and no product is named. Our own figures come from factory component drawings and the factory catalogue.
Will a boiling water tap fit under my sink?
Only if the whole system fits, not just the tap. Ours is three separate units, and in a row they need about 833.2 mm of cupboard width once the working gaps are counted, more than a 600 mm sink base (564 mm inside) or an 800 mm sink base (764 mm inside) offers. The layout that works is the two machines paired in the 800 mm base with the filter moved out.
- What owners report
- A home-magazine guide lists cupboard space first among the problems, and installation guides warn that a fitter may decline a job where the units cannot be fitted with their hoses, cable and cartridge within easy reach. Space is one of the first questions buyers ask before they commit.
- What to check before you order
- Ask for the size of every unit, not a tank size in litres. Measure the clear width between the side panels of your sink base (about 36 mm less than the stated cabinet width in a standard British carcase), and allow a working gap of 25 mm between and beside units for airflow and pipe runs.
- Where our own figures stand
- Boiling machine 188.2 × 188.2 × 260.7 mm; chilled machine 440 × 188 × 306.2 mm (451.7 mm with side service ports); filter 105 × Ø66.5 × 295.4 mm. Paired in an 800 mm base the two machines take 639.9 mm and leave 124.1 mm. These are worked from single-component drawings; the factory has not yet issued a combined in-cabinet drawing.
Can I change the filter without taking the cupboard apart?
Only if the filter housing is fitted with clear space below it. The cartridge is drawn out downwards, so the height under the housing decides whether it is a two-minute job or a joinery job. Ours needs 230 mm of clear space below the filter.
- What owners report
- One owner describes a filter housing fitted so high that the cartridge could not come out without dismantling the cupboard woodwork. It is a fitting error, and it turns a routine service into a job people put off.
- What to check before you order
- Before the fitter drills anything, mark where the filter will sit and measure the drop beneath it. Ask the fitter to leave the housing where you can reach it with the cupboard door open.
- Where our own figures stand
- Filter housing 105 × Ø66.5 × 295.4 mm, with 230 mm of bowl clearance needed to change the cartridge.
Do I need a scale filter, and what happens if I skip it?
In a hard-water area, yes, and it has to be a filter that removes scale, not one that only improves taste. A carbon-only filter does not protect the boiling tank from limescale. Whatever the filter is, ask for its service life in months and litres and whether you can still buy the next cartridge in five years.
- What owners report
- Owners disagree about this. Some in soft-water areas say they never changed the filter and saw no harm. Others in hard-water areas describe scale in the tank within a year and a service call that a scale filter would have avoided. The running cost of cartridges, being tied to one seller, and a cartridge being discontinued all come up.
- What to check before you order
- Find your local water hardness (your water company publishes it by postcode). Ask what type of filter comes with the system, how long a cartridge lasts, whether third-party cartridges are supported, and what the warranty says if the filter is left past its life.
- Where our own figures stand
- The 51008 anti-scale cartridge is serviced every three to six months, or 2000 litres, whichever comes first. Our warranty excludes scale damage where the filter has not been serviced, and treats the cartridge as a consumable. The long-term supply route for cartridges is issued with the trade pack; it is not something we will guess at here.
What happens to the safety mechanism after the warranty ends?
Ask three things before you order: which part stops the boiling control being operated by accident, how many operations it is rated for, and whether it is covered for the whole tap warranty. A boiling tap that fails unsafe is a bigger problem than one that fails shut.
- What owners report
- Owners describe safety parts that wear out with ordinary use, and they worry about a guest mistaking a boiling tap for an ordinary hot tap, especially where the boiling and hot handles look alike. Those worries are sharper once the guarantee has ended.
- What to check before you order
- Ask whether the boiling control is a separate, self-returning control rather than part of the mixer lever, ask for its rated life, and ask what the seller does after the guarantee ends.
- Where our own figures stand
- The boiling control is a child-safe self-returning cartridge and is separate from the mixer control. We have not been given a rated life in operations for that cartridge, so we do not quote one.
What if it leaks or the tank fails, and who supplies the parts?
Ask for the warranty term for each part separately, and for the spare-parts route in writing. Seller troubleshooting guides put most faults in the under-sink units and their seals rather than in the tap, and the complaints that last longest are about help running out once the warranty has.
- What owners report
- Seller troubleshooting guides put leaks from worn seals or loose connections among the commonest faults, and some owners describe replacing a tank or other parts within a few years. The common thread in what they write is less the fault itself than a support route that is slow or absent once the warranty has ended.
- What to check before you order
- Get the term for the tap body, the cartridges, the boiling machine and the chilled machine in writing, and ask who holds spare parts in your country and for how many years.
- Where our own figures stand
- Three years on the tap body, ceramic cartridge and finish; two years on the boiling machine and on the chilled machine. The spare-parts policy and replacement route are not yet fixed, and are issued with the trade pack instead of being invented on this page.
Is the water really boiling, and is there enough of it?
Ask for the temperature at the spout, not the setting in the tank, and for how many drinks you can draw in a row. A temperature quoted for the tank is not necessarily the temperature at the spout.
- What owners report
- Buyers ask whether the water is truly boiling or only very hot, and some owners report an inconsistent temperature or spitting from the spout. One says the supply ran short when several guests wanted a hot drink at once.
- What to check before you order
- Ask for the delivered temperature and the tank capacity, and ask how long the machine takes to recover after a run of drinks.
- Where our own figures stand
- Boiling delivery temperature is 98 °C from a 2.4 litre boiling tank with a 1500 W element. We have not been given a recovery time or a flow rate to quote, so we do not.
Why is the flow weak, and what water pressure does it need?
Weak flow after fitting is usually an airlock, a blocked or exhausted filter, or mains pressure below what the system was built for. Measure the pressure at your isolating valve before ordering, because an older home with a gravity-fed supply may be under the minimum.
- What owners report
- Low flow is one of the commonest complaints in troubleshooting guides. They usually suggest looking for trapped air after a new installation or a cartridge change, then for a blocked filter, then for the pressure at the property.
- What to check before you order
- Have the mains pressure measured, and ask what the system’s minimum and maximum inlet pressure is.
- Where our own figures stand
- The system is specified for a mains inlet pressure of 1.5 to 5 bar.
Is there a socket under my sink?
A boiling and chilled system has two powered machines, so it needs two power points inside the cupboard, and an extension lead in a cupboard with water pipes is not an acceptable answer. A kitchen with no socket under the sink needs an electrician before the fitter.
- What owners report
- Installation guides say the system needs a power outlet within reach inside the cupboard, and warn against extension leads. A socket that sits behind where a machine will stand is as much a problem as no socket at all.
- What to check before you order
- Count the sockets in the cupboard, check they are reachable once the units are in place, and ask which plug or connection the machines use for your country.
- Where our own figures stand
- The boiling machine draws 1500 W and the chilled machine 120 to 170 W. The plug type for the UK is confirmed in writing with the order rather than assumed.
The checklist
Eight questions to get answered in writing
| Problem | Ask the seller | Our published position |
|---|---|---|
| Space | Dimensions of every unit; clear width of your sink base | Three units; paired layout in an 800 mm base |
| Filter access | Clear drop under the filter housing | 230 mm bowl clearance |
| Scale | Scale filter or carbon-only; service life in litres | Anti-scale cartridge, 3 to 6 months or 2000 L |
| Safety mechanism | Separate boiling control; rated life; term after the guarantee | Separate self-returning cartridge; rated life not yet given |
| Leaks and spares | Warranty per part; spare-parts route in writing | 3 years tap, 2 years machines; spares policy not yet fixed |
| Temperature | Delivered temperature; tank size; recovery time | 98 °C; 2.4 L; recovery time not yet given |
| Pressure | Measured mains pressure; system minimum and maximum | 1.5 to 5 bar |
| Power | Sockets in the cupboard; plug type for your country | 1500 W plus 120 to 170 W; plug type confirmed with the order |
Two more limits belong to the whole category, not to any one product: a boiling tap fills a large pan slowly, and it needs mains power and water to work at all. We publish no running-cost or energy-saving figure, because we have not measured one against a stated baseline.
Who wrote this, and what we have not tested
NLB makes kitchen boiling and chilled water tap systems in our own factory in Taizhou, China. The dimensions on this page are worked from our component drawings and the operating data comes from the factory catalogue; both are also published on the specifications page. We have not been given a delivered chilled temperature, a recovery time, a flow rate, a noise figure, an energy figure or the rated life of the boiling cartridge, so none of them appears here. Read the guide to how a chilled water tap works for what the chilled machine does and needs.
For homeowners
Have the cupboard checked before you order
An authorised installation partner in your area measures the cabinet, the sockets and the pressure first, which is the part of this checklist that a website cannot do for you.
Find an installerKitchen fitter or showroom?
Ask for the drawings and for written answers to the eight questions above, for the model you would specify.