New mono mixer tap fitted, hot water flow is slow!

[Koko88]

I have just replaced the old bathroom basin mono mixer taps, 2 tap heads, standard
compression valve type, to a modern mono mixer single lever type.

For some reason the hot water running on the new single lever mono mixer tap is slow flowing compared to the old ones.
The cold water running flow is absolutely fine, no problem whatsoever.

I have also changed the standard isolation valves to the full bore isolation valves which improved the hot water flow just a tiny little bit.

The new single lever mono mixer tap is suitable with low pressure & high pressure, 0.1 bar to 0.5 bar.

The older mono mixer tap had M12 size 15mm copper tap tails and the new tap is supplied with the standard flexible M10 tap tails.

The supplied standard M10 flexible tap tails, 8mm bore is actually only 6mm bore hole as I measured it with digital calliper!

Is it possible to get hold of M10 flexible tap tails with large bore instead of the standard 8mm bore?

Any suggestions on how to improve the hot water flow, the house is has a vented heated system.

Thanks

 

[king of pipes]

Yes it is possible to buy replacement flexible connections with a larger bore or even copper tap tails, but be aware your new tap will be the ceramic disc type and is restricted slightly by the tap cartridge itself as apposed to a seated washer type tap you may well see a slight improvement but don't expect it to match the cold supply . Kop

 

[Koko88]

Yes it is possible to buy replacement flexible connections with a larger bore or even copper tap tails, but be aware your new tap will be the ceramic disc type and is restricted slightly by the tap cartridge itself as apposed to a seated washer type tap you may well see a slight improvement but don't expect it to match the cold supply . Kop

Yes it is possible to buy replacement flexible connections with a larger bore or even copper tap tails, but be aware your new tap will be the ceramic disc type and is restricted slightly by the tap cartridge itself as apposed to a seated washer type tap you may well see a slight improvement but don't expect it to match the cold supply . Kop

Where can I buy replacement flexible tap tails connections with a larger bore?

Googled it and there seems to be only one standard type, all 8mm bore available.

Took the supplied flexible tap tails to the nearest Screwfix & Toolstation branch (both next to each other) to compare with theirs and the bore size is all identical.

Ask the staff and they told me that all the flex tap tails are the same bore size everywhere?

 

[John.g]

You say,
"For some reason the hot water running on the new single lever mono mixer tap is slow flowing compared to the old ones. The cold water running flow is absolutely fine, no problem whatsoever."

Are both the hot and cold supplies gravity fed from the cold water storage tank?

 

[Koko88]

You say,
"For some reason the hot water running on the new single lever mono mixer tap is slow flowing compared to the old ones. The cold water running flow is absolutely fine, no problem whatsoever."

Are both the hot and cold supplies gravity fed from the cold water storage tank?

Yes, both hot & cold water is gravity fed from cold water storage.

 

[John.g]

Can you swap the two tap tails to compare the flowrates then?, or/and measure the flowrates from each tap tail (into a container) while disconnected.

 

[Koko88]

Can you swap the two tap tails to compare the flowrates then?, or/and measure the flowrates from each tap tail (into a container) while disconnected.

I just want to get hold of some M10 flexible tap tails with a wider bore hole than the standard 8mm bore hole if available.

The older replaced mono mixer set had M12 copper 15mm tap tails and the hot water flow rate was fine, obviously not as strong as the cold water flow rate.

The copper tap tails is a lot wider than the supplied flexible tap tails which is the difference.

 

[John.g]

I just want to get hold of some M10 flexible tap tails with a wider bore hole than the standard 8mm bore hole if available.

The older replaced mono mixer set had M12 copper 15mm tap tails and the hot water flow rate was fine, obviously not as strong as the cold water flow rate.

The copper tap tails is a lot wider than the supplied flexible tap tails which is the difference.

I have a similar set up on kitchen (Franke) sink, with 1/2 ins copper tails. I have gravity fed hot water and can either have gravity fed cold or mains cold, I normally run mains cold but just did a test there now with both hot & cold gravity fed, the hot tap flowed 1L in 11.9 secs = 5.04LPM and the cold flowed almost exactly the same, 1L in 12.1 secs = 4.96LPM, I can't see why the hot water flow rate should not be as strong as the cold water as there is practically no restriction in a vented HW cylinder.
I also have a old ceramic cartridge(s) mixer still with the two 0.5M X 6mm flexible tails attached and connected in to both my hot and cold (gravity) feeds. Both flowed almost exactly the same at ~ 2.62LPM, again as I would have expected, if I just run water through either disconnected tail then I get 4LPM, obviously the ceramic cartridge has a high friction loss and installing even 8mm tails will give a appreciable gain in flowrate, and copper tails, even more so but both flowrates, whatever they are should IMO be very similar, my CWST supplies the HW cylinder through a separate outlet from the cold water outlet.

 

[Ben-gee]

You need to get rigid copper tails to see any improvement- buy in any plumber’s merchants. And as above if they are both gravity fed then the hot/cold should behave the same - unless there is a partially closed valve somewhere, or debris in the system.
Did you flush through the pipework before connecting the tsp?

 

[king of pipes]

Where can I buy replacement flexible tap tails connections with a larger bore?

Googled it and there seems to be only one standard type, all 8mm bore available.

Took the supplied flexible tap tails to the nearest Screwfix & Toolstation branch (both next to each other) to compare with theirs and the bore size is all identical.

Ask the staff and they told me that all the flex tap tails are the same bore size everywhere?

For your best chance of improvement use these they are copper tails 8 mm X 15 mm.kop

 

[Koko88]

For your best chance of improvement use these they are copper tails 8 mm X 15 mm.kop

For your best chance of improvement use these they are copper tails 8 mm X 15 mm.kop

Want to use flexible tap tails as it’s a lot easier to install, no pipe work required

I have to go for copper tap tails, this is more or less the only option available that is cost effective.

 

[Koko88]

Want to use flexible tap tails as it’s a lot easier to install, no pipe work required

I have to go for copper tap tails, this is more or less the only option available that is cost effective.

 

[John.g]

Don't see any reply attached.

 

[Koko88]

I have installed new M10 copper tap tails to the new mono mixer taps and the improvement on the hot water flow rate is hardly noticeable!

The old replaced mono mixer taps had M12 copper tails so bore hole size not significantly any larger.

I am beginning to think it’s how the the new mono mixer tap is made/designed, restricting the hot water flow if pressure is low, everything narrower inside?

The old mono tap mixer probably wider inside with better flow so it’s very frustrating with all this messing around by replacing the isolation valve to full bore & copper tap tails without really solving the problem.

Maybe I should try different mono mixer taps but my guess they’re all probably all the same with modern design, everything compact and narrower!

 

[John.g]

But, the cold water flow is/as was? greater than the HW flow?, if so can you just measure the flow from each when detached from the mixer tap just in case there is some restriction in the HW supply.

 

[Ben-gee]

In post #1 you said the tap was suitable for 0.1 bar to 0.5 bar - this is an unusual range to be stated.

Are you sure it is not 1 bar to 5 bar?

5 bar is a common maximum pressure rating.

I suspect you have a high pressure tap.

There are lots of low pressure mono taps out there that perform satisfactorily at 0.2 bar, which is probably the pressure you have.

 

[John.g]

Again, "The cold water running flow is absolutely fine, no problem whatsoever." (post #1), the crux of the problem?
The tests I carried out, admittedly on a two tap mixer at a 0.6bar (downstairs) head was exactly 2.62LPM (each) with the 6mm tails attached and 4.0LPM with tails detached, probably a hi pressure tap, these 1/4 turn taps do have very narrow outlet slots, the main port is I think ~ 10.5MM.
Based on the above, would expect only ~ 1.5LPM upstairs at a 0.2bar head.

 

[Koko88]

In post #1 you said the tap was suitable for 0.1 bar to 0.5 bar - this is an unusual range to be stated.

Are you sure it is not 1 bar to 5 bar?

5 bar is a common maximum pressure rating.

I suspect you have a high pressure tap.

There are lots of low pressure mono taps out there that perform satisfactorily at 0.2 bar, which is probably the pressure you have.

In post #1 you said the tap was suitable for 0.1 bar to 0.5 bar - this is an unusual range to be stated.

Are you sure it is not 1 bar to 5 bar?

5 bar is a common maximum pressure rating.

I suspect you have a high pressure tap.

There are lots of low pressure mono taps out there that perform satisfactorily at 0.2 bar, which is probably the pressure you have.

 

[Koko88]

Just checked the specification, instruction leaflet on the mono mixer taps, it’s compatible with both low & high pressure, 0.1 to 5 bar, so my mistake when I said 0.1 to 0.5 bar!

 

[Koko88]

But, the cold water flow is/as was? greater than the HW flow?, if so can you just measure the flow from each when detached from the mixer tap just in case there is some restriction in the HW supply.

 

[Koko88]

I have tested the flow, detached both the hot & cold supply pipes from the new mono mixer

The hot water flow is fine, even reconnected it back to the old mono mixer, the hot water flow is a lot stronger than the new mono mixer as previously stated.

 

[John.g]

Can't find your txt with above,

Got it now, can you measure the exact flowrates now from both the hot and cold attached to the Tap (normal)

 

[Koko88]

What is measuring the exact flow rates on hot and cold going to help/solve the problem?

Apart from knowing the flow rates figures/specs & etc, the hot water flow still going remain the same, regardless?

I am thinking of trying another set of mono mixer taps with 2 individual lever, hot & cold, compression valve type than ceramic to see if there’s any difference.

 

[Ben-gee]

The best flow will come from a compression valve tap.
I have seen a cut away mono mixer with “lift and turn” cartridge- the pathway from where the tails screwed in to the underside of the cartridge was a 2mm channel through the brass.

 

[John.g]

What is measuring the exact flow rates on hot and cold going to help/solve the problem?

Apart from knowing the flow rates figures/specs & etc, the hot water flow still going remain the same, regardless?

I am thinking of trying another set of mono mixer taps with 2 individual lever, hot & cold, compression valve type than ceramic to see if there’s any difference.

IF, as you said originally, that the cold flow is absolutely fine with the new Tap but the hot is not fine then ( and you have proved that there is no restriction in the supply) to me that points to a faulty Tap which may be replaced FOC if still within warranty and knowing the two flowrates will strengthen your claim, Now, I don't know what absolutely fine means in your book but I have a bathroom basin tap fed from 2 X 1/4 turn taps which I presume are of the cartridge type and from the CWST head of ~ 0.2/0.25bar gives a hot flowrate of 4.04LPM and a cold flowrate of 4.48LPM, both fine by me, you can compare your cold flowrate with this, if you wish, and if happy with it and if you are happy with the single lever Tap then I would look at replacing it with a similar type, hopefully, FOC.

The above does show that there is a huge difference in LP and HP designed Taps as the old 2 tap mixer I tested a few days ago will only flow ~ 1.5LPM at a 0.2bar head, both Hot and Cold.

 

[Koko88]

IF, as you said originally, that the cold flow is absolutely fine with the new Tap but the hot is not fine then ( and you have proved that there is no restriction in the supply) to me that points to a faulty Tap which may be replaced FOC if still within warranty and knowing the two flowrates will strengthen your claim, Now, I don't know what absolutely fine means in your book but I have a bathroom basin tap fed from 2 X 1/4 turn taps which I presume are of the cartridge type and from the CWST head of ~ 0.2/0.25bar gives a hot flowrate of 4.04LPM and a cold flowrate of 4.48LPM, both fine by me, you can compare your cold flowrate with this, if you wish, and if happy with it and if you are happy with the single lever Tap then I would look at replacing it with a similar type, hopefully, FOC.

The above does show that there is a huge difference in LP and HP designed Taps as the old 2 tap mixer I tested a few days ago will only flow ~ 1.5LPM at a 0.2bar head, both Hot and Cold.

I am going to take the mono mixer, single lever back to Screwfix later and swap it for another mono mixer with 2 lever/heads, hot & cold, compression valve type.

Have to wait and see if there’s any improvement!

 

[Koko88]

I am going to take the mono mixer, single lever back to Screwfix later and swap it for another mono mixer with 2 lever/heads, hot & cold, compression valve type.

Have to wait and see if there’s any improvement!

 

[Koko88]

Went back to Screwfix, exchanged the single lever type mono mixer for the 2 head type, compression valve mono mixer taps & fitted them to the new basin yesterday.

The hot water flow is now back to normal just like it use to be!

It’s either the compression valves or having 2 tap heads made all the difference or a combination of both!

The only downside is the returned single lever mono mixer taps looks more modern, slicker in design & looks!

 

[Ben-gee]

It’s the compression valves, see post #24, this is not new to us!

 

[John.g]

It would be interesting to compare the new 2 Tap compression type flowrates with the 4/4.5 LPM from my upstairs 2 Tap 1/4 turn type.

 

[Be kind]

You say,
"For some reason the hot water running on the new single lever mono mixer tap is slow flowing compared to the old ones. The cold water running flow is absolutely fine, no problem whatsoever."

Are both the hot and cold supplies gravity fed from the cold water storage tank?

I’ve got exactly same problem. I have to put my finger over tap hold to make pressure better for bubbles