Hot water tap in kitchen has low flow, but the bathroom hot tap flow is fine

[E.S]

I have been having trouble with my hot water tap in the kitchen lately. The flow rate had been dropping over the past few months to the point where it completely stopped running at all. My boiler is an old hot water cylinder, so water pressure is essentially not meant to be great for the hot. But it used to be a lot better than it is just now, when I moved in.

At first I thought it was the tap as it was quite old, so I replaced it. After doing so, the water started coming out again from the hot tap... but not how it should be.

It then seemed after replacing the tap and getting the flow back on the hot, the flow was slowly starting to reduce down again slowly. Whilst the hot tap in the bathroom was still running fine.

I then flushed all the water out the system for the house and checked the isolation valve underneath the sink to see if there was any blockage, There was none. However there was a very small amount of limescale build up where the tap pipe connects to the isolation valve. I attempted putting a screwdriver through the valve to see if there was a blockage behind the valve and still couldn't find anything.

I connected the pipes back up and turned on the main water supply. But when I went to turn on the hot tap in the kitchen again, the flow was even worse than before I flushed the system, just an hour before that. Yet the bathroom tap hot flow is still fine!?

Does anyone have an idea as to why this is happening? I don't understand how the flow in the bathroom (which is farther away than the kitchen tap) can be fine but the kitchen is not, especially when the valves seem OK. Do I just need to get a pump to increase the flow to the kitchen hot tap? Or is there possibly another valve somewhere in the walls/under floorboards that could be clogged?

P.S I have tried holding my thumb over the tap in the kitchen and pushing water back up the pipes to try and release any airlocks. But this didn't seem to do anything to help either.

 

[Christopher buzzard]

Have you got a picture of the tap? Have you checked the filter bit on the end of the tap spout?

 

[Chewitt]

As per previous comment it is worth checking the aerator on the spout.

It is worth checking the minimum head bar pressure on the tap. If it is a cheap mixer from eBay etc it might need a minimum 1 bar pressure on the hot supply.
Is your home a house, bungalow or flat?.
Do you have a tank in the loft or a fortic combination cylinder.

 

[Tim Furneaux]

It could be a pressure imbalance between the hot and cold, your kitchen cold will be straight off the mains at mains pressure but hot is probably no more than 1 bar. Meaning if you have a mixer tap that doesn’t balance the pressure the cold will stop the hot coming out. If the imbalance is bad enough mains cold can feed into your hot water cylinder. Best way to check is isolate the cold to the kitchen tap to see if it affects the hot flow rate. This won’t be an issue in your bathroom as the cold won’t be mains pressure.

 

[E.S]

It could be a pressure imbalance between the hot and cold, your kitchen cold will be straight off the mains at mains pressure but hot is probably no more than 1 bar. Meaning if you have a mixer tap that doesn’t balance the pressure the cold will stop the hot coming out. If the imbalance is bad enough mains cold can feed into your hot water cylinder. Best way to check is isolate the cold to the kitchen tap to see if it affects the hot flow rate. This won’t be an issue in your bathroom as the cold won’t be mains pressure.

What you are saying makes sense. I noticed when I fitted the new tap that the hot water would stop coming out when i turned on the cold. I thought that this was because it wasn't a mixer tap as advertised. I contacted the seller to complain, but I might have to apologise and say I will keep the tap and try to fix my water pressure instead.

I tried isolating the cold tap and turned on the hot tap but it was still the same low pressure coming out of it.

The tap does also have an aerator which may be causing a problem as well.

 

[galaxy_plumbing]

Im on with debris in aerator. Unscrew it and run hot water

 

[Tim Furneaux]

Hopefully it is debris in the aerator as that’ll be an easy fix, but if the tap is new it’s unlikely. As asked before do you have a combi boiler or hot water cylinder, if cylinder i assume it’s on the first floor, how long’s the pipe run to the kitchen, is the bathroom tap plumbed using 22mm rather than 15 hence better flow? If it is poor pressure reducing the frictional loss from iso valves, lots of elbows in the pipe run or changing to 22mm pipe will all help but some of those will get expensive/time consuming...

 

[E.S]

It is a new tap so it is unlikely it's the aerator, I also have a tap that has a nozzle that can be rotated and angled and can also change to shower stream, so I am unsure how to remove the aerator. It is just a hot water cylinder that I am using. I am actually in a ground floor flat and my boiler sits at the same level as my floor in a cupboard in the living room. And the pipe running to the kitchen tap is about 7 metres in length. The bathroom taps also have 15mm pipes connecting them so they are the same as the kitchen taps but further away from the boiler than the kitchen.

Would it be OK to put a water pump of about 1 bar onto the hot water supply for the kitchen tap or would that cause problems within the system?

 

[JCplumb]

Oops, I replied to a post that is no longer there, I was AFK for a couple of hours before I hit reply