Slow cold water through hot tap

[Logicearl]

We have a problem which has left us scratching our heads over, including the plumber who has just changed our boiler and installed new taps etc.
Everything is working fine apart from the washhand basin hot tap situated in the upstairs bathroom. It seems very slow when turned to full, warms up slightly after 30 seconds or so, then gets colder, and stays that way.

What could be causing this? The plumber thinks its a problem with the tap. All the other taps seem to be working fine.

System:
Worcester Bosch Greenstar 34CDi Classic - running at 1 bar
Taps (in question) Bristan Hampton basin mixer

TIA

 

[Masood]

The 1bar pressure at the boiler is the system pressure, not the pressure of the supply to the tap. What's the cold water like at the same tap? Your plumber should disconnect the hot water pipe below this tap and check pressure and flow. If it's low and slow, there's likely a problem with the pipework. If it's good, then the tap is at fault.

 

[Logicearl]

Ok, thanks, I'll let him know your comments.
The water from the cold tap has the same flow as the hot.

 

[Masood]

Ok, thanks, I'll let him know your comments.
The water from the cold tap has the same flow as the hot.

Same as with the hot - check pressure and flow in the pipework to the tap, that'll tell you whether it's the tap or not. I'm surprised your plumber hasn't thought of this though?

 

[lame plumber]

could be cold main pressure into house is too low, or mispiping the pipework on change over or lots of other issues any decent plumber could sort in 5 mins!!!!!!!

 

[erj]

do you have a mixer shower fitted, had them mixe the cold into the hot. if not check pipes

 

[Logicearl]

do you have a mixer shower fitted

Yes we had a grohe euphoria shower fitted at the same time. Hmm.

 

[lame plumber]

never get the truth first time!

 

[jfb]

Has the tap got flexible connections are they kinked or twisted??

 

[Logicearl]

Has the tap got flexible connections

Yes I think so, will check these suggestions out tomorrow, thanks guys.

 

[Logicearl]

I've had a look behind the pedestal and found that the tap has indeed flexible connections, but on top of that, I notice that the tails, if thats what there called, seem to be too long, so they have both been coiled in a loop before entering the tap. Could this be a good enough reason for the problem?

 

[erpkid]

I've had a look behind the pedestal and found that the tap has indeed flexible connections, but on top of that, I notice that the tails, if thats what there called, seem to be too long, so they have both been coiled in a loop before entering the tap. Could this be a good enough reason for the problem?

Looped is OK but not pretty. Kinked is what would could cause the slow flow.

 

[Logicearl]

Can someone explain, how the plumber would check the pressure and flow? Is it some form of kit, which all plumbers would/should have?

 

[Masood]

Can someone explain, how the plumber would check the pressure and flow? Is it some form of kit, which all plumbers would/should have?

Yes, he should have the relevant equipment, especially as he has installed a combi boiler. Measuring flow rate is part of the commissioning procedure. The process should not need explaining - he should know how to do it. Are you sure it was a plumber doing the work and not DIY?

 

[Logicearl]

He is GS registered, I've checked. So although he may well be registered, it doesn't mean we get a better, safer service then? Or maybe he has cut corners, hmmm. Thing is he came recommended, lol. Looks like I need to have a few words with him. He seems to be content on blaming the tap without trying any of the options mentioned here.

I've just looked at the benchmark on the commisioning paperwork, and the water flow rate has been marked as 11l/min.

 

[Masood]

He is GS registered, I've checked. So although he may well be registered, it doesn't mean we get a better, safer service then? Or maybe he has cut corners, hmmm.

Not suggesting that he cut corners, just a little surprised that he hasn't thought of these things himself.

He seems to be content on blaming the tap without trying any of the options mentioned here.

I've just looked at the benchmark on the commisioning paperwork, and the water flow rate has been marked as 11l/min.

Well maybe he has done flow and pressure checks at the basin tap, and that's why he's sure it is the tap? You say all the other taps are fine. Presumably the previous basin tap was OK as well, and you say there are no kinks in the flexible hoses.

Unless he's done pipework alterations in the supply to the basin, then his diagnosis isn't necessarily wrong, just that other things should be checked as well, to rule them out. Maybe he has checked already.

Oh - just thought - a lot of new taps come with flow restrictors to save water. Have they been left in? I always remove them...

 

[Logicearl]

He did strip the tap down, and according to the tap diagram there is whats called a flow regulater, but couldn't find one/it. Bristan have now said it should be removed, which is strange, as there isn't one installed, lol.

 

[Logicearl]

Just to update you guys on the successful outcome.

It transpires that the fault was down to one of the 3 internal holes underneath the cartidge, that was partially blocked by a metal bur, from when it was drilled.
We only found this by taking the whole tap apart.

I must mention that Bristan at first told us to remove the plastic flow regulator, which should have been underneath the cartidge, but infact there isn't one, full stop. A second person at Bristan then stated that maybe we should remove the grill, which is where the water flows down the spout, but again we couldn't as its non removable. In the end we found the problem to be a manufacturing and QC fault.

Also I must point out that the diagrams on the Bristan website, in relation to the tap, differ from the actual tap. In the diagrams, it shows this flow regulator, it also has it as an option to purchase as a spare. So any potential purchaser beware, as you could end up on the phone for a considerable amount of time. I think they ought to sort out the product details better, keep them up to date, and make sure that people answering the phone, also know the products they make/sell.

Does this sort of thing happen alot to you, as plumbers?

 

[Howsie]

Thanks for the update. Always nice to know what was causing the problem instead of a dead thread.

 

[Masood]

Thanks for the update. Always nice to know what was causing the problem instead of a dead thread.

Agreed, always nice to know the outcome. Bristan have always been pretty decent quality in my experience, and customer service is helpful. Shame your experience has not been as positive.