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

 

[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