Bizarre hot water/shower issue top get your teeth in to

[plumbobsqarepip]

Hi Guys

ANY suggestions greatly appreciated

I Had a callout to a job where the mixer shower started running cold (the system is an unvented indirect cylinder, and cold is mains fed). So naturally checked the fillters and hot water pressure which were fine, and after being unsuccessful in finding a replacement cartridge deemed they needed a new mixer. Replaced the mixer but still have the same problem. Again checked the basins hot tap next to the shower which was fine, and then put a cap on the cold and turned water on to check adequate flow to the hot which was fine again.

HEEEEEELLLLPPPPP (thanks in advance)

 

[Puddle]

Sounds like maybe mains cold pressure maybe over powering mains hot pressure,check any balancing/regulating valves,maybe a separate one on the dedicated cold supply and someone been tampering with it

imho

 

[plumbobsqarepip]

havent checked any reg valves yet puddle, will do today tho. Even so, there is really nothing in it between the cold and hot on the basin next to the shower? and flow seems great at shower end, or is it presure as opposed flow?

cheers

 

[CES]

Is there any inline filters (small cone shaped) that fit into the inlet pipe before the mixer valve? It seems strange that the HW to the basin is fine, if you can trace the pipe between the two and you cant see anything then I would test the flow from the HW pipe using a bit of hose and a valve on the end. Remove the mixer and see what flow of HW you get

 

[plumbobsqarepip]

Hi CES

yep have done all of that, checked fillters, and took the mixer off capped off the cold and turned water on,..... hot had great flow!

 

[CES]

Put a press gauge on the HW and see what you get, then test the cold. I would agree with Puddle, sounds like a balancing issue, there should be a balancing valve connected to the inlet to the unvented system and ideally the cold water supply should have been taken off this valve to get a balanced supply.

 

[vectra65]

Had this one before mixer was fitted work ok for 6 or so months i got a call out had a look in the end found that somone had turned stop tap up running full bore over powering hot may be that

 

[Deleted member 25704]

First check if hot and cold pressure are balanced. This means that the mains cold distribution is fed via the same pressure reducing valve as the hot. Many unvented systems have hot at 3 bar pressure, but mains may be 6 causing the difference in pressures.

Now, if the mains cold is higher pressure than the hot, and if there are mixer taps fitted, or other shower valves, then it could be that one of the internal check valves on one of the mixers is stuck open on the hot side. This allows crossflow of mains water at say 6 bar, into the hot distribution, which will create problems for showering.

Solutions include fitting a single check valve on each hot water entry to mixers - do one at a time and check - and/or fit a pressure reducing valve on the incoming mains above the stop-tap and make all the system balanced pressure. Hence no potential for cross-flow.

 

[plumbobsqarepip]

All great advice guys thanks, am going this arvo and will let u know how i get on.

 

[Deleted member 25704]

It will be cross-flow on one of the mono-block taps, so check these first.

 

[plumbobsqarepip]

if they mono taps are turned off, how will they effect the shower? they cant cross flow if there off?

 

[Deleted member 25704]

if they mono taps are turned off, how will they effect the shower? they cant cross flow if there off?

That is what you have now learned...they can.

Many shower valves and mono block mixers have mixing chambers. This is one of the key reasons why balanced pressures are desireable.

I have come across this problem on combis as well!

 

[plumbobsqarepip]

That is what you have now learned...they can.

Many shower valves and mono block mixers have mixing chambers. This is one of the key reasons why balanced pressures are desireable.

I have come across this problem on combis as well!

Thanks clanger


Ive been back and stuck a presure guage on (like i should have the first time) the hot at 3.5 and cold at 7..... so put a PRV just after the stopcock and still same problem??? any ideas..

oh yeh left the prv at factory settings

 

[Deleted member 25704]

Thanks clanger


Ive been back and stuck a presure guage on (like i should have the first time) the hot at 3.5 and cold at 7..... so put a PRV just after the stopcock and still same problem??? any ideas..

oh yeh left the prv at factory settings

Isolate all the taps and showers if possible and check one by one. I would look for b&Q type mono-blocks first.

You may be lucky here, if there are service valves fitted below taps.

 

[plumbobsqarepip]

Isolate all the taps and showers if possible and check one by one. I would look for b&Q type mono-blocks first.

You may be lucky here, if there are service valves fitted below taps.

Yeh i'm sure there are service valves there, BUT, now the hot/ cold are balenced i.e. at 3.5bar, I shouldnt have a problem with cross flow should i?

 

[stevetheplumber]

my bet is unballanced supplies test by running a couple of cold taps at the same time as the shower see if it is mixing then

 

[stevetheplumber]

just re read what youve said did you put the preasure reducing valve on the incoming main or on the supply to the shower only
if its on the incoming main youll still have unbalanced supplies

 

[plumbobsqarepip]

just re read what youve said did you put the preasure reducing valve on the incoming main or on the supply to the shower only
if its on the incoming main youll still have unbalanced supplies

Hi Steve

On the incoming main, surly there cant be that much in it? and how come it worked for the 2 or so previous years?

have also been back and isolated all mixers... still no joy:svengo:

 

[Deleted member 25704]

Hi Steve

On the incoming main, surly there cant be that much in it? and how come it worked for the 2 or so previous years?

have also been back and isolated all mixers... still no joy:svengo:

Plumbing is stochastic art, which means dealing with problems that are not of your own making. There is never an answer to a plumbing problem like this, because there is always something we don't know!

Damage limitation with diagnosis - its good practice to fit prvs where monoblock taps are concerned. Most of these taps operate at max 5bar operating pressure - so you have prevented further problems from occuring and assured correct performance of taps in future.

There may another shower mixer in the house, check for ensuites and utility/garage etc

Make sure the hot is on left and cold on right of existing shower valve

 

[plumbobsqarepip]

Plumbing is stochastic art, which means dealing with problems that are not of your own making. There is never an answer to a plumbing problem like this, because there is always something we don't know!

Damage limitation with diagnosis - its good practice to fit prvs where monoblock taps are concerned. Most of these taps operate at max 5bar operating pressure - so you have prevented further problems from occuring and assured correct performance of taps in future.

There may another shower mixer in the house, check for ensuites and utility/garage etc

Make sure the hot is on left and cold on right of existing shower valve

Yep only 3 mixers, its a small house, think ill try what Steve said and turn on all colds and see what i get, at least i know what im looking at then... only problem is, even though i have explained the situation, the customer has made me now take of the new mixer and replace for the old as they are sure its still working!??! hope it is still working or this may be a very long job...

much appreciate your advice by the way guys

 

[WaterTight]

Are you charging by the hour/visit or did you agree a fixed price for a shower swap and are now losing money on each visit?

 

[plumbobsqarepip]

Are you charging by the hour/visit or did you agree a fixed price for a shower swap and are now losing money on each visit?

well was per hour but after the first 'shower swap' didn't work I stopped charging. The way I see it is they shouldn't have to pay me to learn something new, and i'm happy to work for free if i'm learning (up to a certain limit obv). besides dropping in between jobs isn't that much of a hastle really.

 

[stevetheplumber]

something learnt is never a waste

 

[plumbobsqarepip]

something learnt is never a waste

exactly