Loss Of Hot Pressure on New Bath and Mixer Tap

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Hi All.


Would appreciate any advice on below problem\situation - desperate to get sorted and job signed-off!

Sorry for length, wanted to add all detail.



Customer had existing bath and mixer tap with a shower head that apparently worked fine as a shower. Cold is mains pressure, hot is gravity fed via what I think you call a vented system(?)


I swapped the bath and fitted new mixer\head. Span the bath round so tap-end was at opposite end - better suited for new shower screen - I simply extended supply and waste pipes from existing positions.

Cold supply is and was via 15mm copper.

Hot was off a 15mm "T" from a main 22mm pipe. It went through a 15mm elbow and another 15mm "T". Off this "T" was a drain valve and the other outlet of the 15mm "T" went to the hot water tap - via a 15/22 and short length of 22mm copper pipe. All appeared old and as if provided at time of original build. As customer said all worked fine, I cut back to the 15mm, extended to the new mixer via 15mm - before a final 15/22 near the tap.

Customer reports new mixer is unusable, no hot water pressure for shower!!!

My understanding is\was that the throughput of any pipe is governed by the smallest bore on the run - and thought if I made all my run out of 22mm my overall flow's governed by the short length of 15mm anyway - which previously worked fine?

I fitted service valves and flexi hose with install, am to return and check these are fully open and not twisted; as well as putting old shower head back on, 'cos tiny new one has about a quarter of the spray holes as the old one - a restriction?


In the past, when doing simple swap-outs of mixer taps, I get the same complaint. Then find that strainers\filters fitted in the mixer tap for the shower hose connection restricts flow, and removing gets rid of any complaints. This unit seems fully sealed with a rotating base for the hose. All internals seem to be ceramic.

Any ideas?

Or what are my options..... hopefully not having to chop the 22\15\22 "T" out and replace with 22mm throughout - hopefully? :-(
 
I never put a mixer valve on unbalanced supplies, it almost never works because the cold pressure always overpowers the hot gravity pressure, if a customer asks me to do it then I tell them it will most probably not work as a shower and watch their faces when I am proved right at the end of the job :roll: .
 
I never put a mixer valve on unbalanced supplies, it almost never works because the cold pressure always overpowers the hot gravity pressure, if a customer asks me to do it then I tell them it will most probably not work as a shower and watch their faces when I am proved right at the end of the job :roll: .

Hi Chr15.

Thanks for your reply.

I'm learning mixers as showers are nothing but problematic and will have to adopt this attitude in future.

My problem is, I can't tell this customer that - 'cos the old one worked satisfacory. And that's my issue, I see old units working fine for many years as showers, as soon as cusomters buy new ones and have them fitted then there problems start.

Anyone know why?


Cheers,
Neil
 
Hi there,

Is this a combined bath mixer / shower hose with a pull up plunger to switch to shower.

If so it sounds as though the mixer is only suitable for high pressure systems, ie combi / un-vented.
If this is the case you will never get it to work properly unless you pump the hot supply.

You have a couple of options for this. You can either source another new mixer sutiable for low pressure systems, pump the hot supply, fit a "pressure equalizing valve" on the bath mixer supply pipework.

Rico
 
Hi there,

Is this a combined bath mixer / shower hose with a pull up plunger to switch to shower.

Rico

Hi Rico.

Yes, it is a combined bath mixer / shower with a pull out switch to divert output to the shower head.

As long as I can eliminate the previous 15mm hot supply pipe being at fault - so I don't go through loads of effort and agro to change to 22mm only to find it resolves nothing - then I'll have to look at other causes. Assume there must be mixers for low-pressure, and that I'll have to get customer to swap the item?



Cheers for your help,
Neil
 

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