Hot water scolding out of taps and shower

[bt83uk]

We have recently moved into a victorian house (circa 1900), and noticed that the hot water from the Valve shower and taps become scolding hot, as if there is no temprature regulation.(you don't have to have the taps fully open for the temprature to continue rising)

We had a plumber out who wanted to change the shower, as he said the thermostatic/mixer valve had gone, a second opinion suggested it was the tempreature control/heat exchanger on a 15 year old Vaillant combi boiler, and it would be better off replacing it. After a third and fourth opinion and quotes to replace the boiler, we did just that, and have replaced it with a Vaillant EcoTec Pro 28.

The problem still exists... so we are now wondering what the cause could be, we are a bit of a loss, and have had suggestions that the flow rate could be a cause (it's 8l/m from the kitchen tap, and 11l/m from the outside tap which is nearest the boiler). Was the origianal guy correct and it's an issue with the shower(and taps) and they need replacing? Could there be dirt/limescale in the pipes, or just something else?

I have checked both inside and outside stopcocks which are fully open. I have run some temp tests, and the cold water temp is 23degrees, and hot tap it is 63-65 degrees before being consistant at that temp.

We plan on ringing up Thames Water to check the flow rate outside, but are prepared to be told that it's all within acceptable limits, the pipe feed into the house looks like has been changed previously from Lead to Plastic.

Any thoughts, comments, suggestions would be most helpful.

 

[cross thread]

turn the temp down on the boiler

 

[bt83uk]

thought about that but the operating instructions say to not set the water temp below 60 degrees to protect against legionella. I'm a bit loathed to do that, but it does seem like the obvious thing to do.

 

[endecotp]

So it’s set to 60 on the boiler but you’re measuring 63-65 at the taps. That sounds reasonable to me, if pipe runs are short and insulated; there will be some error in both readings. If you don’t like it that hot, just turn the boiler setting down to whatever you want.

You don’t really need to worry much about legionella with a combi; it’s only really a concern with systems with a storage tank. But there are other health concerns with too-cold hot water - your washing-up water is supposed to be as hot as you can bear (with gloves on) in order to not give yourself food poisoning.

If the shower, or a mixer tap, is not able to mix the hot water (of whatever temperature) with the cold to give the temperature that you want, then that’s another problem; either the shower or mixer tap is broken or perhaps there could be a pressure issue.

 

[flameport]

protect against legionella.

The boiler won't cause that.
Of more concern is that the 'cold' water entering your house is 23 degrees - far too high.

 

[dilalio]

Where did you measure that cold temp?
Does the boiler fire when you run just cold?
If yes, then you have crossover somewhere.