Slow hot tap in kitchen

Cloth_of_Gold

We used to have separate hot and cold taps in the kitchen but when we had some work done a while ago we replaced the sink and changed the taps to a monobloc. Since then the hot tap has run very slowly and a recent change of tap hasn't rectified the problem; if anything it's worse. I timed it and it takes around 40 seconds to fill a litre bottle. The plumber suggested having a pump installed but I believe that these can be noisy.

What I don't understand is why the hot water was flowing ok before we changed to a monobloc but it isn't now. The flow in the bathroom basin and bath is ok. Does anyone have any suggestions as to what might be causing this and does a pump sound like the best solution? The hot water tank is in a cupboard next to the kitchen.

FreeBear

If there are isolation valves under the sink, check that they are both fully open.

Is your hot water from a gravity system (hot water cylinder & header tank in the loft) ?

ThisIsWeird

And do you know the makes and models of the new taps? Do you know where they were bought from?

It sounds as tho' your hot supply is gravity, but your cold will be 'mains', so at a much greater pressure. Your tap may be designed for this high pressure, so just not suitable.

Your hot cylinder is in your kitchen, which I presume is on the ground floor, but is your house a bungalow? Where is your cold water tank - in the loft?

You can get tiny pumps that should help, but best if you can avoid them - buzzy wee things...

Kiran

The monobloc tap is restricting the flow rate of the hot water. The old tap presumably had a 15mm supply to it? Your new monobloc will have something like an 8 or 10mm at most. Presumably the cold is incoming at mains pressure to the kitchen tap? What kind of hot water supply do you have, combi boiler, system boiler vented unvented etc? 

PixelPound

Taps have a minimum pressure rating (due to internal design, you might have 8mm or 10mm tails on but the internals can be narrower). I assume that your hot water is gravity fed vented and probably about 0.5 bar (if distance between your tap and the storage tank in the loft is 5m in height), if it's not then could be another issue. Many monobloc taps have ratings above 1 bar, so whilst separate you had hot water flowing fine, you'll only have a trickle in the new.

You need to check and if your hot water pressure is low then either move back to separate taps or replace the monoblock with one that has a lower rating.

PixelPound

Just to add. We had two taps when we bought the house and had the same problem when put in a monoblock. We put up with it, but after 6 years the tap developed a leak, so when I got a replacement, ensured min pressure was low enough. You find that old single taps have minimums below 0.1bar.

Cloth_of_Gold

Thanks for all the replies. I'll come back with the answers asap.

Rdwill

Hi.

I had exactly this when we built our extension and installed a new quooker in the kitchen and a new monoblock in the ensuite.

I couldn't understand why the old hot tap was fine, but with my new setup the hot water was dismal. I proved to myself that it was the new kit, by disconnecting the hot from both appliances and attaching them to a hosepipe that went outside. When turning on the hot at the isolator the flow was as expected.

So I deduced the bores within the new kit were smaller than in the existing. Unfortunately to remedy I had to install a pump on the hot water, which is a little noisy, and not ideal.

The other solution was to source kit with a wider bore, but I don't think it is made anymore, especially on quooker type equipment, all new equipment is now built for pressurised systems.

Not the news you want, but I hope that helps.

ListysDad

Taps are a PIA. There is no specification for what constitutes Low or High pressures so manufacturers can put on a box whatever they like as all they are interested in is flogging you some brassware.

If you still have a hot water cylinder in an airing cupboard then you have a low pressure hot water system. If its a bungalow then fitting any 'modern' (quater turn tap or single lever) tap will deliver poor flow results. End of. The issue is that ceramic disc taps (1/4 turn & single lever) create a very small hole through which water flows. What you need in those circumstances are the old school 'multi turn taps' as they open internally much more so can let more water flow through.

For homes with floors, its often possible to put a ceramic disc type taps on the ground floor as the water is 'driven' harder by the higher head pushing it. For teh upper floors though its the same situation.

When choosing ceramic disc taps for a low pressure hot supply, you have to ensure (by asking the manufacturer) the tap delivers at 0.1 bar. ANYTHING lower will reduce flow rates.

Lastly, the cheap sh1te isolation valves fitted by all idiots now severely reduce flow. Whilst they fit on 15mm copper, the internal water way is reduced to around 5mm and is poorly machined. All taps, no exceptions, should have decent 'full bore' isolators fitted so flow is maximised.