Hot water tank not keeping heat

ForestBluebells

Ok I’m still confused, I had it turned on for the full recommended 90 minutes last night and I could still use just the hot tap, it was warm but perfect temp only using the hot tap on its own so hasn’t heated the tank much more? My in house reading device of electric usage also looks to have stayed the same (whether this is accurate or not now I don’t know with octopus go as I have not had my first bill yet)…. Even more confused now!

Bendy_House

Have you 100% confirmed that the analogue timer is switching reliably as it should be?

I don't suppose you have a way of checking for 'live' voltages to confirm the immersion is getting power when it should?

Does yours have a manufacturer's name on it anywhere? Does it have an 'override' switch on the side or top?

These pegs still look barely moved from the 'off' position to me. Perhaps it's the way that model is, but every other one of these devices I've seen have a FAR more clear amount of movement in them - the 'on's and 'offs' are very obvious.

ForestBluebells

Let me move the timer on to see if my in house display changes 

ForestBluebells

Turning the timer to the “on” period did make my in house monitor show higher usage 🤷‍♀️

ForestBluebells

There is an on/auto slider on the side, is set to auto. But when I rotate it to set to the “on” time it does seem to draw more power although I can’t hear any click it just slightly pushes some bit of plastic up

Section62

ForestBluebells said:

Ok I’m still confused, I had it turned on for the full recommended 90 minutes last night and I could still use just the hot tap, it was warm but perfect temp only using the hot tap on its own so hasn’t heated the tank much more? My in house reading device of electric usage also looks to have stayed the same (whether this is accurate or not now I don’t know with octopus go as I have not had my first bill yet)…. Even more confused now!

What do you mean by the BiB @ForestBluebells ?

Are you talking about a mixer tap at a sink or bath which only runs hot enough when the hot 'tap' only is on?  Or do you mean you only get hot enough water from one tap at a time.  I think you mean the former, but just want to exclude another possibility with the latter.

Do you have some kind of anti-scald device on your hot water system?  The kind which mix hot and cold water together with thermostatic control, so the 'hot' can't get too hot?  They vary in appearance a lot, but often look something like this one -
https://www.toolstation.com/thermostatic-mixing-valve/p18520

...if you do, there's a chance that could have gone wrong and isn't letting enough hot water through.

ForestBluebells

No it’s an old system, house was built in the 70s and just has a hot tap and a cold tap that I then have to try find the right mix of. Usually the hot water would be too hot just using the hot tap and need cold mixed in so not to burn, currently I’m only turning on the hot tap and it’s warm but not hot

Section62

ForestBluebells said:

No it’s an old system, house was built in the 70s and just has a hot tap and a cold tap that I then have to try find the right mix of. Usually the hot water would be too hot just using the hot tap and need cold mixed in so not to burn, currently I’m only turning on the hot tap and it’s warm but not hot

The Megaflo is relatively modern though... so someone has had the system upgraded at some point.

So to confirm, you have two separate taps each with its own outlet/spout into the sink... not a mixer tap with just one spout?


I think your next move should probably be turning the immersion heater on (now) and leaving it for a couple of hours to see if the water gets as hot as it should.

If it doesn't, I think I'd suspect a faulty thermostat.

I also noticed that the tabs on the timer didn't look like they were out far enough, but I'm not sure that is the problem as if they aren't out sufficiently to switch on the heater then you'd get no additional heat at all. And after a few days you'd now have a tank of barely lukewarm water. The fact the water heats up but not hot enough, suggests the system is working, but cutting out too soon.  To me that means either too short a heating period, or the thermostat is not working as it should.

ForestBluebells

The tap on the sink is separate hot and cold with separate spout and the shower separate hot and cold tap that combine up the shower hose so i turn the taps individually. I’ll put it on now and see if it gets hot. I think it will as I heated it for just 15 minutes one afternoon and had a hot shower. Something is seemingly causing this to not heat properly earlier in the morning. I’ll check my energy usage logs tomorrow when they are available and compare to the previous day too

coffeehound

One other thing to check:  while it is heating, have a look at the tundish to check whether any water is being discharged -- it should look something like this