It costs more than you think to spend a penny. Water (and sewerage) bills are the country’s forgotten utility - the average cost is set to rise to £390 and many pay substantially more.

Yet it is possible for many to save £100s on this with just five minutes work.

From 1 April, water bills in England and Wales go up by an average 1%.

Yet dig in the figures and some will have bigger hikes, like customers of Dee Valley who face 5%.

Water is a funny industry. It is privatised, but there’s no competition. You can’t switch supplier – although there is a discussion for this to happen, with an outcome later this year.

Instead, to save, it’s all about what works for you.

1. Does your home have more or the same number of bedrooms than people?

If yes and you’re in England and Wales, then you should definitely check out whether you can save by switching to a free water meter. In Scotland, there’s a fee, which usually means it’s not worth it, and in Northern Ireland there’s no need for a meter as water is free anyway.

That’s because water bills are based on rates – roughly the value of your house from way back in 1989. The bigger your house, the more you pay, but the fewer people in it, the less you use. So switching from a bill based on your house value to a meter that measures your usage is worthwhile for those with spare rooms.

To find out exactly if you’ll save by switching to a meter, use the calculator at ccwater.org.uk, which assesses your usage such as how often you use the dishwasher, washing machine, shower or tub.

Just keep an eye on your bills to check your saving, and if not you can usually switch back after 12 months or a month after your second bill, whichever is later – check with your water firm before you sign up.

However, there are some who have been forced to get a meter – in which case you don’t have a right to switch back.

2. Is it worth switching?

Typically, two people in a four-bed Thames Water home paying £450 could save £150 every year by switching to a meter.

Some save even more, as Jeannie tweeted me: “@MartinsLewis changed to a water meter 1 year ago following your advice. Saved £492 in in one year, thanks.”

And this from Suzanne: “@MartinsLewis I have saved £240/year installing water meter. Ta!”

Yet water rates mean you know exactly what you’ll pay, regardless of usage. So, if the saving’s less than 5%, think carefully before switching.

3. What if you’re not allowed a meter?

Water companies can argue it is ‘justifiably impractical’, eg, in a tall flats block with shared water pipes. If this happens, and you think a meter would save, ask how much your ‘assessed charge bill’, which is based on how many live in your flat and water usage, is. Better still, if that happens, you can choose whether to pay this or the rates – so go for whichever is cheaper.

4. Do you have a soakaway?

If you live in a small town or village and have a ''soakaway'', ie a pit of gravel that collects surface rainwater, you'll send less water through the sewers and should ask for money deducted from your bill.This is usually between £20-£50/year and can be claimed whether you're on a meter or not.

5. Cut your water use

For those on a water meter, saving water means saving cash. But cutting water use also helps the environment and saves others money too – paying to heat water squirts away £140 of a typical annual energy bill. So these tips can be useful even if you’re on a rateable bill.

  • Grab water savings freebies worth up to £30. Lots of gizmos can help douse your bill. Whether on a water meter or not, you can get freebies from water companies that’ll help use less water – check their website or call them.

These can include aerated shower heads, which pump air with the shower to make it feel high pressure but using less water, or bath buoys a toy you can put in the bath to use less water. For a bigger list of who does what go to mse.me/water.

  • If it’s yellow, let it mellow. If it’s brown, flush it down. I don’t really need to explain this one – I think you get it. I’ll be honest it’s not one I do, but many people do do (sorry). At the very least, if your loo has two buttons, try to only use the big flush when necessary.
  • Save your washing up for one wash. Instead of washing up as you go, save it and do it in one go to minimise the amount of water used.
  • Steam your veggies. It’s healthier and tastier than boiling them and uses a lot less water too.
  • Load up the washing machine, but not the kettle. Wait until you've a full load before using your washing machine or dishwasher. Some new washing machines use fewer than seven litres of water for each kilogram of clothes, while modern dishwashers can use as little as 10 to 15 litres of water a cycle. But don’t fill the kettle if it’s just for one cuppa (big energy saver that too).
  • Bundle into the bath. Get up close and personal with your other half and share your bath. Or put the kids in together to save water.
  • Check your meter doesn’t turn when the water’s off. If does, get leaks sorted pronto. See a handy guide from Anglian Water at http://tinyurl.com/h636wf6 and many firms off free leakyloo stickers, which you put on the back of water devices and if they fall off you’ve a leak.