Hot tap flows noticeably slower than cold.

[Steve57]

I have an unvented hot water supply.

On my mixer tap in the kitchen, hot water only flows slightly less than the cold. However, I have just fitted new mixer taps to the bath and basin in the bathroom. Again, the bath hot tap flows slightly slower than the cold but it is really noticeable at the basin where it is probably a third to a half as much as the cold. It also hisses as if the valve is only just cracked open. It isn’t. I have swapped the hot and cold feeds over at the flexible hoses and they are both equal in flow. Both valves are new and fully open. Is it a faulty tap, is it normal or can I somehow increase the hot water flow throughout the house generally?

 

[JTplumbingservices]

I have an unvented hot water supply.

On my mixer tap in the kitchen, hot water only flows slightly less than the cold. However, I have just fitted new mixer taps to the bath and basin in the bathroom. Again, the bath hot tap flows slightly slower than the cold but it is really noticeable at the basin where it is probably a third to a half as much as the cold. It also hisses as if the valve is only just cracked open. It isn’t. I have swapped the hot and cold feeds over at the flexible hoses and they are both equal in flow. Both valves are new and fully open. Is it a faulty tap, is it normal or can I somehow increase the hot water flow throughout the house generally?

 

[JTplumbingservices]

If ive picked you up correctly you’re saying you have disconnected the flexi’s and are getting an equal flow directly from them ?
If that’s correct then it will be an issue with the taps.
I’m also assuming you didn’t have bath and basin taps on at the same time to check the flow?
Do you have a balanced cold supply to the bathroom from the valve at the cylinder ?

 

[Best]

Also check that a piece of solder or other debris has got into the tap cartidge.
(Even if you weren’t soldering, turning water off and then back on can disturb particles)
Some of the mixer taps cartridges will partially block with just a tiny ‘ball bearing’ of solder

 

[Steve57]

Thanks for the replies so far. Fairly certain that there are no debris in there - I did make one solder connection before both taps were connected up as well as fitting new valves and gave each one a good squirt through the valves to release any debris that may have been there. Before swapping the pipes, I disconnected both flexis and blew back through the tap to check in case anything was in there.

When I swapped the feeds and each flow was checked separately, although they had near equal flow, the flow was reduced on the cold and increased on the hot which makes me think the cold is flowing faster than the hot.

Regarding the balanced flow, is this the valve that does it? If so, how can I adjust it?

 

[Best]

You can’t adjust balanced flow. That combination valve has a balanced cold outlet solely for cold to taps which is same pressure as cold to the unvented cylinder.
Don’t touch anything on that valve or the unvented unit unless you are G3 qualified in unvented systems

 

[Steve57]

Oops! I Googled that valve and came up with Caleffi cold water balance valve and showed how to adjust it. I flipped the little grommet out of the end of the grey handle and turned the Allen key in the direction of the '+' whilst running the kitchen hot water tap. The flow increased. It was now the same as the cold flow. Checked my bath, basin and downstairs loo hot taps and now they are all the same flow as the cold. Better than they’ve ever been! Have I made a mistake? Shall I leave as it is, put it back to where it was or get a G3 guy in to check it?

 

[JTplumbingservices]

Oops! I Googled that valve and came up with Caleffi cold water balance valve and showed how to adjust it. I flipped the little grommet out of the end of the grey handle and turned the Allen key in the direction of the '+' whilst running the kitchen hot water tap. The flow increased. It was now the same as the cold flow. Checked my bath, basin and downstairs loo hot taps and now they are all the same flow as the cold. Better than they’ve ever been! Have I made a mistake? Shall I leave as it is, put it back to where it was or get a G3 guy in to check it?

The idea of the balanced supply off that valve is so the pressure to cold taps is the same as the pressure to the cylinder and therefore the hot water pressure so for example at a mixer valve you don’t have unequal pressures. It sounds like you’ve adjusted the pressure setting of the valve which would change both hot and cold pressures equally if the balance cold is coming off it too the taps, and you shouldn’t be messing with that unless competent.

 

[Best]

Oops! I Googled that valve and came up with Caleffi cold water balance valve and showed how to adjust it. I flipped the little grommet out of the end of the grey handle and turned the Allen key in the direction of the '+' whilst running the kitchen hot water tap. The flow increased. It was now the same as the cold flow. Checked my bath, basin and downstairs loo hot taps and now they are all the same flow as the cold. Better than they’ve ever been! Have I made a mistake? Shall I leave as it is, put it back to where it was or get a G3 guy in to check it?

Turn it back in the direction of ‘ - ‘ approximately same amount of turns that you did earlier to reduce the pressure and contact an unvented qualified plumber to come out and set it properly. Get them also to service the unit as shouldn’t cost extra really.
Should be serviced once a year to keep all working safe and have full warranty.
That combination valve is one of the main safety components of unit.

 

[townfanjon]

Please get this checked , you have no way of knowing what pressure you have adjusted it to without a gauge .

 

[Steve57]

It's back to as it was now - I did note how it was before tampering. Thanks all - I’ll just put up with it until I can get someone round. No big deal as I’ve lived with it since the system was converted so I’ll just wait until my boiler needs it’s first service in a few months time and get it all looked at then.

Just out of curiosity, what could have gone wrong - reading up online (could be all cobblers, I know), the part I tampered with was the balancing valve, yes? It's to get the hot and cold running at the same flow rates specifically when you have mixer taps. The red part in the picture is the safety valve and if things go wrong, it should let water out which I should see in the tundish? I did suspect the hot flow was not as strong as the cold as when I had the shower flow turned down, it went cold instead of staying the same temperature. Anyway, no harm done hopefully and a valuable lesson learned.

Is the G3 qualification something most central heating engineers hold or am I likely to need to get two separate people round?

 

[townfanjon]

Not all heating engineers are G3 , when you find someone ask them if they are G3 if they “um and r “leave them alone .

 

[mubesjnr]

Firstly, like all other contributors have remarked you must get a G3 qualified plumber to work on this for you. Especially, as you might actually have a partially balanced hot and cold supply......I'll be precise;

Lets say you might have a mains feed in to the house that is at quite a high pressure, say in excess of 3bar, and this then supplies a single or multiple draw off downstairs which then rises up to the combination valve by the unvented cylinder.

This is then pressure reduced and then a balanced cold comes from the combination unit to a single or multiple draw off upstairs. Not uncommon if the unvented cylinder has been retro fitted without a complete and full pipe work refurbishment.

Hot will come from the cylinder at this (new) pressure as a consequence of cold feed to the cylinder passing through the combination valve but if compared to the incoming mains water draw off downstairs which is coming into the house unchecked, will qualitatively seem to be at a lesser pressure and poorer flow.

Therefore you can see that unless these variables are identified by a qualified individual you will not be able to accurately determine what the likely cause is for the lack of flow/pressure/customer satisfaction etc?

Go to the Gas Safe Register website and find and engineer via its search facility for finding an engineer. Then go on his profile and you will be able to see if he has G3 qualification....marked as vented and unvented cylinders. But what ever you do never touch that combination valve or you could have this on your hands:

PS. I have nothing to do with Plymouth Plumbers Ltd

 

[Steve57]

Frightening! Yes, my system was converted to a sealed heating and unvented hot water about 18 months ago - I got a certificate for the hot water from Gas Safe at the time. As far as I could tell, all they did was connect the cold feed in the loft to the pipe that used to come out of the cold water tank. My hot water cylinder is downstairs in the airing cupboard. The boiler was then changed about 7 months ago (by a different firm) and I asked them to check the unvented at the same time. I don’t know if they did - all I got was a certificate from Gas Safe for the boiler - should I have got something for checking the unvented too? Didn’t get any receipts for the work but also got a 7 year guarantee letter from Vaillant as it was fitted by a Vaillant installer. As said, it’s back where it was until a specialist can check it out when the boiler is due it’s first service but isn’t that what the safety valves are for? It seems that I have two - one on the valve itself and another one on the hot water tank. They are both joined to a T joint that then goes to the tundish. Would I see some leakage in that if anything was amiss?

 

[Best]

Get the unvented unit serviced.
They usually have a 25 year guarantee on the cylinder and this depends if you have a full yearly service record.
Obviously proper servicing by a G3 plumber will keep the unit safe and working properly and the plumber would know if anything was piped wrong

 

[mubesjnr]

As the contributor with the profile pic of a Churchill Tank above rightly re-iterates get it checked by a G3 qualified engineer, of which I detailed how you can obtain one in my earlier thread.

For what it's worth, I think you have a retro fitted unvented cylinder served by a 15mm mws (mains water supply) rising to the loft joined to the old cold feed with a partially balanced H & C supply to multiple draw offs.........but I can't be sure or accurate about that statement as this needs to be investigated on site.....which returns me to my opening sentence.

By the way, the service that you allude to in respect of the new boiler will probably not include the cylinder. Therefore, returning again to the advice about a G3 engineer, get them in now in order to satisfy your conundrum.

Good luck and regards.

 

[Welder]

The GSR is not the only place to find a G3 engineer. If you look around this site you will find a place to request a plumber. Simply ask that they are G3. Personally, I'd be looking for someone who has been G3 for a minimum of 5 years.

I'm picking up on your 'hissing'. Exactly where is that coming from? Although it may sound like the tap, have listen to see if its from the iso valve. Are you iso valves full bore ? How much did you pay for them?

 

[Best]

As the contributor with the profile pic of a Churchill Tank above rightly re-iterates get it checked by a G3 qualified engineer, of which I detailed how you can obtain one in my earlier thread.

For what it's worth, I think you have a retro fitted unvented cylinder served by a 15mm mws (mains water supply) rising to the loft joined to the old cold feed with a partially balanced H & C supply to multiple draw offs.....but I can't be sure or accurate about that statement as this needs to be investigated on site...which returns me to my opening sentence.

By the way, the service that you allude to in respect of the new boiler will probably not include the cylinder. Therefore, returning again to the advice about a G3 engineer, get them in now in order to satisfy your conundrum.

Good luck and regards.

Well observed, - Churchill tank!

 

[mubesjnr]

Better that I suppose than the ponderous Matilda! How on earth we came out on top with armour such as that I'll never know??