Hi @Domthtc ,

I think we can answer this, but to be sure please post photos of all your meters so we can check them.

Thanks!

These are the meters, thank you. THTC is labelled on top left one.

Something’s missing there I’m afraid. Either that isn’t a THTC setup, or you didn’t include all the meters.

Can you look around for anything else that might be a meter or a switching device?

The two meters above are outside the house.

The set up inside is as follows:

I was switched over from SSE last year.

According to my OVO account details, the DOM (bottom right meter) is “Anytime” and the THTC meter (top-left) is “Heating”.

I switched off my water heater as you can see in this photo, the switches in down position are the water. The DOM (bottom-right) meter in the previous photo continues to flicker. The top-left THTC meter is off and doesn’t run down. 

I am confused however as my water seems to be continuously running (there is a constant noise) despite it being switched off. It is only supposed to come on at certain times. That’s why I switched it off. 

So am I correct in saying that the THTC meter is the one for the water heating?

THTC would be the heating/hot water one - DOM is for general purposes. If wired correctly, your hot water would ONLY be on the THTC meter - you may want to ask an electrician to check. There might be a fault somewhere in your setup...

It looks as if there are two elements in your water heater. The main one is at the bottom of the tank, governed by the RTS and working only in offpeak periods. The other is near the top and always live along with the rest of the stuff on the Anytime circuit*. This means that if you run out of hot water between offpeak periods, you can heat up enough for a bath, say, using the top element - a so-called boost function. This should of course be used sparingly, because it will use a lot of electricity at peak rate. 

There should be a switch near the hot water tank to activate this function, or it may run on a thermostat that automatically keeps the top third of the tank hot. However, with both the water heater breakers off at the consumer unit (the ‘fuse box’), neither element should be drawing power. Are you sure that the noise you hear is that of water heating in the tank, or could it be coming from a switch - a clockwork timer, perhaps - near the tank? 
 

*   The Anytime circuit is what uses the meter with the DOM label - probably meaning ‘domestic’.  There is no convention about what to call or how to label these circuits, so we sometimes see Normal and Low, Day and Night, Continuous and Switched, Peak and Offpeak. It gets even more confusing when there are more than two circuits. This is the first time I’ve seen DOM to cover everything except heating. 

Thank you for the info. That’s very helpful.

There is a thermostat with a boost function in the kitchen.

The noise I hear is from upstairs, like water constantly flowing or being heated. During the winter, I only heard this noise after I had used the hot water in one of the kitchen or bathroom sinks, or after running a bath when it refilled and reheated. I also heard it come on during Off Peak times, as you mentioned.

Now, however, I hear this noise constantly, which is why I have switched off the heating at the mains. This has stopped heating the water, but the sound of the water flowing or being heated remains. It’s strange.

@Domthtc

What you describe sounds like it’s the cold water fill for the hot water tank. probably a cold water ‘header’ tank which then fills the hot tank as needed.
They are often in the loft, but may be in the cupboard above the hot tank.

The constant running water noise will be because the ballcock / inlet float valve from the mains is sticking, worn or broken. (It’s like the one in your toilet cistern).
They do their job for years with no thought about them, but the sealing washers do wear out over time and need to be replaced

So cold water from the mains is constantly filling the header tank and running straight out again through the overflow- and that’s what you can hear running like a running tap.
If you check around outside of the property you may be able to see/hear where it’s coming out of the overflow pipe.

If your water is metered then constant running like that is costing you money on your water bill.

You need a plumber to look at the header tank and fix the inlet valve.
TBH it’s a fairly simple DIY job if you are handy.
First try would be to just joggle the arm up and down to free it if it’s sticking, it that doesn’t stop it overflowing then:
You could just replace the washer if that is all it is, a new washer costs pennies.
But sometimes the float may be cracked and full of water so needs replacing, or you may just prefer fitting a whole new valve and float, cost under a tenner.
Here’s a video of how to fit a whole new one, you can also see where the washer goes if you just want to replace that.
(A plumber will charge you a lot more of course).
https://www.youtube.com/watch?v=WuC9uaPzneM&ab_channel=CharlieDIYte

Thanks, I haven’t noticed any water dripping outside, so not sure if that’s what the sound is.