Martin Lewis has shared his “rule of thumb” for determining if Britons can make savings on their water bill.

His rule of thumb as helped many people, including Debbie, save hundreds on her yearly water bill.

On the Martin Lewis Money Show this week, Debbie and her husband explained that after watching a previous episode of the money show, they found out they may be able to get cheaper bills.

She said: “The bill before the water meter was installed was roughly about £712. We said let’s do what we were doing anyway because that’s when we’ll find out the true reading.

“My two bills after the water meter was fitted was just over £234. Giving me a massive saving of £473. Almost £500 and I’m going to let anybody and everybody know.”

Labelled the “forgotten utility,” the money saving expert explained there are three ways to save on water England and Wales.

Water bills are based on the 1990 rateable value of a house. So those in a bigger house will likely be charged more, even if there aren’t many occupants in the house.

In this situation, Mr Lewis explained a water meter that measures one’s usage is likely to be cheaper.

He said: “I have a rule of thumb on this. If you have more bedrooms than people in your house, you’re almost certainly and should be using a water meter.”

As Debbie and her husband lived in a three-bedroom house, they knew they fit the criteria and thought to check if they can change.

Commenting on Debbie’s huge savings, Mr Lewis said: “£480 big saving right? That was over six months. That’s £960 a year do not ignore checking your water savings.”

If people fulfil Martin’s rule of thumb they should go onto CCWater.org.uk to check if they too can make water bill savings.

Water firms will give customers an assessment of how much water they will likely use.

In most places, customers have two years to change back if the meter doesn’t work for them, however, other places will not allow a change back so he urged people to check with their company before signing up.

If they say fitting it is not practical – Mr Lewis suggested customers ask for an assessed charge.

Providers will assess what one’s costs would have been if they had a water meter. So if someone’s assessed charge is higher than their water bill they should opt for that and vise versa – whatever is cheapest