Shower Cold, plumbers clueless

[AWK]

shower cold unless hot sink or bath tap turned on for a few seconds.
shower then remains hot for about a minute then goes cold.
Original shower Mira minilite evs, replaced with an Aqalissa bar type....
still same problem. Using a megaflow unvented system with mains cold direct to shower, spoke to a plumber on phone... he aint got a clue..HELP.

 

[Burger]

I would say possibly cold forcing hot out of the way or maybe even the valve has been fitted incorrectly as in reversed supplies.

 

[Riley]

Hot left cold right? Or as said has a check valve failed?

 

[AWK]

Hot left. Same problem with new shower!!!

 

[Burger]

Hot left. Same problem with new shower!!!

So you had the same issue with the Mira minilite?

 

[Mastermixlee]

May be that the unvented cylinder pipework hasn't been done correctly regarding the balanced cold supply.
I'd recommend getting g3 cert engineer to check it out.

 

[AWK]

been working fine for 20 yrs, problem started about 3 weeks ago.

 

[Riley]

Then something has changed have you removed the shower and run the water is it a noticeably different flow from H&C??
Are you getting ok hot at all other outlets

 

[townfanjon]

If you have any mixer taps anywhere and they have isolation valves , turn them off , failing that you might have to fit some

 

[AWK]

all taps ok only the shower has problems, could Anglia water have changed the incoming pressure from somewhere out there???

 

[Riley]

Would affect your other taps then wouldn’t it.

 

[Riley]

Your mains SHOULD come to a combi block next to the unvented cylinder and be balanced so you get equal h & c everywhere. Is your kitchen tap a mixer?

 

[Burger]

been working fine for 20 yrs, problem started about 3 weeks ago.

I’m not picking, but that would have been helpful from the start, moving on... what has changed plumbing wise in the last 3 weeks? Or have you had any work carried out?

 

[AWK]

yes kitchen tap is a mixer. nb before fitting new shower I purged the lines and the cold had a lot more pressure than the hot.

 

[AWK]

the only work that was done prior to all this was a radiator drain cock replaced,

 

[Burger]

yes kitchen tap is a mixer. nb before fitting new shower I purged the lines and the cold had a lot more pressure than the hot.

Could be the kitchen tap. This will be fed from the main and not balanced from the unvented, except the hot. Theoretically it could be the same, but a pressure reducing valve may have been used? Also when was the shower replaced?

Try isolating the kitchen tap altogether if isolation valves are fitted, then try running the shower.

 

[AWK]

fail too see how the kitchen tap would affect it as it would not be used when showering, I fitted the new shower a few days ago.

 

[Riley]

Ok don’t take our suggestion. It could be that the cold is forcing its way back up the pipe in the tap body toward the cylinder. It may not be that but you have to find the possible failure points

 

[Burger]

fail too see how the kitchen tap would affect it as it would not be used when showering, I fitted the new shower a few days ago.

It doesn’t matter if it’s being used, I once came across a kitchen tap install, whereby the kitchen tap wasn’t being used, yet the tank in the loft was overflowing because it was backfilling into the tank, which was caused by a failure in the tap. Usually on unbalanced supplies.

 

[Riley]

The two things I’d try;
Isolate the kitchen tap and see if that helps
Take the shower off the wall and see if you get hot water out of the hot side

 

[AWK]

fair points, i'll try isolating the kitchen tap but it wont be till tomorrow, thanks for all your help, i'll post result, cheers.

 

[townfanjon]

Post 9 !!!!

 

[Roy_66]

Is your shower cold feed from upstream or downstream of the combination valve that Riley mentions above ? (Downstream would seem best to me)



**video removed we do not offer any advice on working on unvented cylinders even via you tube as you need to be G3 qualified to do so***

How old is it ?

 

[Harvest Fields]

shower cold unless hot sink or bath tap turned on for a few seconds.
shower then remains hot for about a minute then goes cold.
Original shower Mira minilite evs, replaced with an Aqalissa bar type..
still same problem. Using a megaflow unvented system with mains cold direct to shower, spoke to a plumber on phone... he aint got a clue..HELP.

How can a plumber diagnose over the phone?
Answer he cannot especially if not unvented trsined. Get a G3 trained engineer in to have a look if it hasn’t been fixed already.

 

[AWK]

Go to the top of the class CBW1982 AND RILEY, mixer tap in bathroom sink causing problem... isolate one side and water out of both. just had a hot shower YIPPEE. Thanks guys.

 

[Riley]

Go us

 

[AWK]

how do I give you guys a rating?

 

[Riley]

Badges below each post

 

[Aire]

Go to the top of the class CBW1982 AND RILEY, mixer tap in bathroom sink causing problem... isolate one side and water out of both. just had a hot shower YIPPEE. Thanks guys.

You do realise that @townfanjon suggested this an hour after you posted your question, and you dismissed him straight away saying your other taps were fine. Try listening to the experts next time your given good free advice.

 

[AWK]

I do apologise townfanjon, missed that. u just got a winner tick.

 

[townfanjon]

I do apologise townfanjon, missed that. u just got a winner tick.

Shakes his head , lol . I will pm you my bank details.