Domestic questions that are burning and unanswerable in more or less equal measure are a staple of social media. This week, it was towels. Specifically, how many does an adult human need to own? The podcast host Abdul Dremali asked, and more than 2,000 Twitter replies later, he still couldn’t go shopping for towels. There are some household jobs that no one knows if they are doing right. So can the experts settle a few domestic debates?

1 How many bath towels does a household need?

Each family member should have their own. “You can’t share a towel,” insists Lynsey Crombie, AKA Queen of Clean from Channel 4’s Obsessive Compulsive Cleaners. She thinks this means that five bath towels are necessary per person. But this is because she has a high towel turnover: she washes them every other day, “if not after every use”. The cleaning expert Aggie MacKenzie is more relaxed, saying she relies on “a sniff test” to know when a towel needs washing, but even she will not let a towel exceed “three or four days” of usage. They may be out of step, though. A poll of 3,000 people by Hubbub, an environmental charity, found that people washed their towels every 11 days. Sally Bloomfield, a professor of hygiene at the London School of Hygiene and Tropical Medicine, says that towels and bed linen need to be “hygienically cleaned” at 40C, despite the environmental benefits of a 30C wash. If you are dropping the temperature, using a powder product or tablet, she says, will “boost the hygiene efficacy” because it contains active oxygen bleach. Bloomfield thinks a weekly towel wash would suffice, but reiterates: “Don’t share towels.” To extend the time between washes, avoid putting towels on top of each other and let them dry out after use. Anna Watson, the head of advocacy at CHEMTrust, thinks a towel could go two weeks between washes.

Cleaners’ verdict: Five towels per person, each washed every few days.
Environmental experts’ verdict: Two, each washed once a fortnight.

2 How often should you change your sheets?

I wash my bed linen once a week. At least, I think I do. But given that my washing day has fallen on almost every day of the week, I think I may miscount. This isn’t too bad. Crombie thinks once a week is sufficient. She does her whole household’s linen on a Sunday – unless someone has a bug, in which case she does it daily. In her TV work, she has visited homes where sheets have been left unchanged for two months, and says the smell is disgusting. MacKenzie, who was arguably the forerunner of the Insta clean phenomenon, agrees. Apparently, the aroma is unmistakably greasy and sour. As she points out: “The less you change sheets, the more bits of skin will be in the bed.” She recommends a weekly bed change (pyjamas every few days), but for children’s beds – or if there’s not much “traffic” in your bed – a fortnightly switchover is acceptable. Using a top sheet between your body and the duvet means that the duvet cover can be washed once a month, she says, and the mattress protector “when it looks dingy”. I look mine in the eye once a year, but Crombie washes hers, and the pillow protectors, weekly. The key is to make sure that you have a full load and use eco settings, says Stephanie Hurry from Waterwise, which works for greater water efficiency. Chad Staddon, a resource economist at UWE Bristol who is “interested in people’s behaviours around water”, says he could last two weeks, but his wife prefers a weekly wash. The Hubbub poll found that, on average, its respondents changed their sheets every 16 days. Bloomfield says that pets’ bedding needs to be washed as often as human bedding – but not at the same time.

Cleaners’ verdict: Once a week.
Environmental experts’ verdict: Once a week is reasonable.

3 Can shoes be worn indoors?

“In my house, I don’t like people to wear shoes,” Crombie says. She also dislikes bare feet indoors; one of her pet hates is seeing the imprint of a sweaty foot on a wooden floor. However, if guests come to a dinner party and “the shoes are part of the outfit”, they can stay on the feet. I fear I could spend a long time trying to evaluate how integral shoes are to a look, so this acid test may not suit all personalities. In any case, if a guest wears shoes indoors, Crombie recommends washing the floor as soon as they have left – but, she laughs: “I’m not normal!” MacKenzie, who has co-authored a new cleaning book called The Miracle of Vinegar, also likes shoes to be removed at the front door. Bloomfield says that floors are a low risk as a transmitter of germs, and is unmoved either way. Watson at ChemTRUST says that she likes shoes to be removed. Heather Poore, the creative director at Hubbub, says she removes hers. But Stephen Munton, the director of the Domestic Cleaning Alliance, disagrees. “A floor is there to be walked on,” he says.

Cleaners’ verdict: No.
Environmental experts’ verdict: No. But this is a matter of personal preference.

4 How often should you wash your jeans?

“If jeans are only worn in the house and not outside, I will wear them again without washing. But if I’ve worn them out and about, they need to be washed,” says Crombie, whose book How to Clean Your House is published next month. “They hold on to a lot of germs,” she adds. This contradicts the advice of many denim manufacturers. Levi’s CEO once revealed that he didn’t wash his jeans for a year. MacKenzie says she can get eight to 10 wears out of jeans without washing them. The Love Your Clothes campaign recommends freeze-washing: putting the jeans in the freezer for 24 hours, although this doesn’t remove stains. “Personally, I would put mine in the wash every couple of weeks,” says Hurry from Waterwise. “You want to be thinking about the amount you are washing clothes,” says Watson. Last year, Friends of the Earth found that clothes washing generates about 4,000 tonnes of plastic microfibre pollution in the UK every year. Making sure the drum is full helps, as this reduces friction between clothes, making them shed fewer plastic fibres.

Cleaners’ verdict: Every one to 10 wears.
Environmental experts’ verdict: When they are dirty.

5 Is it OK to use a toilet brush?

It had never occurred to me – nor the environmentalists interviewed – that there might be another way to clean a toilet. But MacKenzie says this is an issue that needs to be addressed. She would never let a toilet brush enter her house. “Toilet brushes give me the heebie-jeebies. I think it’s because I have seen so many in my time,” she says. “I can’t bear them. I just think they are vile.” Bloomfield agrees they are unhygienic. Crombie owns a silicone one without bristles. “There is a fetid liquid bacteria soup at the bottom of every toilet-brush holder,” MacKenzie points out. Until now, I have always accepted toilet brushes as one of life’s necessary inconveniences, but MacKenzie says she “would much rather get a pair of thick rubber gloves on and use my fingernail under the thick rubber gloves to get any bits”. Even though she has said the words “thick rubber gloves” twice, they are still not putting a thick enough layer between me and the image of the fingernail on the toilet bowl. Crombie also advocates donning the rubber gloves for “a sweep round any sticky bits with some toilet paper”.

Cleaners’ verdict: Toilet brushes are not to be trusted.
Environmental experts’ verdict: This is not an environmental issue.

6 What is the best way to wash a cleaning cloth?

Cloths that are used to clean somehow always seem inherently clean themselves. This is wrong, of course. Especially the ones that curl in a slimy heap by the tap. “Cloths are a wonderful spreader of germs. Oh, they are fantastic!” Bloomfield says. Crombie goes through a staggering 16 cloths a day, all colour-coded. Other than the toilet cloth, which goes in a tub on its own, she washes them all in the machine at 60C, adding a bit of Dettol Laundry Cleanser to the mix. She washes tea towels after each use. Some people, she says, and my face grows hotter as she says this, have a habit of folding used tea towels as neatly as possible and hanging them on the oven like a good deed. Those towels are dirty, she says. MacKenzie loves microfibre cloths. To clean them: “Get a bowl of boiling water, add a capful of bleach and dump the cloth in,” she says. How often? “I’d say at the end of each day. Once you’ve wiped down your surfaces.” Hurry says that she “would usually give it a rinse or a wash after each use. Then when it was starting to look a bit too grubby, I’d throw it away.” Watson at CHEMTrust never buys a cloth. She makes hers out of cut-up holey children’s clothes, and sticks them in with the clothes wash every other day.

Cleaners’ verdict: Wash after each use. Minimum of daily.
Environmental experts’ verdict: Rinse after use. Wash every other day.

7 How often should you dust?

“There are chemicals in all our products, carpets and furniture,” Watson says. “Those chemicals get abraded off and build up in household dust. You want to stay on top of that.” She suggests once a week to dust surfaces. “To try to reduce your exposure to chemicals that are present in indoor air, trying to keep your house as dust-free as possible.” This seems tricky because in my house the dust seems to regroup barely an hour after it has been dusted. I use a dry e-cloth duster. “Can I just say, that’s where you’re going wrong,” MacKenzie says. “Damp. No polish,” says Munton, who is actually dusting as we speak. He uses a cheap cotton flannel, then a terry tea towel to buff.

Cleaners’ verdict: Once a week.
Environmental expert’s verdict: Once a week.

8 How often should you vacuum under the bed?

“More often than you think,” MacKenzie advises. “I’d say every few weeks. Or, if you have asthma, probably every few days.” Crombie, who has “a lot of vacuums”, likes to do her bedroom daily, and says: “If you have the ability to pull out the bed easily, then do it every time you Hoover. Otherwise once a month.” Access is clearly a factor here, and this may be why the Good Housekeeping Institute replies to say: “Ideally once every three months.” “Hmm. I’m afraid to say that it’s really important to be thinking about those places in a house where dust accumulates,” says Watson. “I’m not saying once a week. It depends if you’ve got a bed that’s off the floor. If it’s fairly accessible, do it. Chemicals build up in thick dust.”

Cleaners’ verdict: Daily to every few weeks, depending on access.
Environmental experts’ verdict: Weekly if you can access the space. Otherwise, as often as you can manage.

9 How often should you deep-clean the bathroom?

Deep cleaning means different things to different people. “We find that people tend to be driven by visual clues,” says Staddon diplomatically. “Once a week?” The Good Housekeeping Institute agrees: “At least once a week, but if there are people with bugs or small children around, then daily.” Bloomfield thinks a toilet should be cleaned two or three times a week, to stop the spread of germs, while Crombie performs “a five-minute challenge” on her toilets every day: “Wipe the sink over, wipe the toilet seat and pan, a bit of bleach, quick wipe of the bath, open the window. I can do it in four minutes 30,” she says with some satisfaction. On top of that, she does a weekly deep clean lasting half an hour. “Swish something around at least once a day,” says Munton, who is out of breath from lugging a vacuum down a staircase. He likes to clean toilet seats with washing-up liquid. “It’s the best. It’s pH-neutral. It’s cheap. Everybody’s got some.” Hurry from Waterwise is circumspect. “This is one we wouldn’t dictate,” she says. “But with the right sort of products and a bit of elbow grease, you wouldn’t need to use a lot of water.”

Cleaners’ verdict: Daily toilet clean plus a weekly deep clean of bathroom.
Environmental expert’s verdict: As you see fit.

10 Is it best to shower in the morning or evening?

In the morning, MacKenzie says. In the evening, Crombie says. She likes “to go to bed clean”. Her husband “is the other way round … He’ll do a full day’s work, travel on the tube, then undress and get into my bed. Whereas I think if you go to bed clean, you get up clean.” Munton showers morning and evening. Hurry prefers morning showers, especially ones that are four minutes or shorter: the average shower uses eight to 12 litres of water a minute. Some power showers go up to 15 litres a minute. Reducing the products you use will limit the amount of time you spend under the water. “A shower is water plus energy and that’s invariant,” says Staddon, whose gran used to flake off the lye soap with a penknife, and give Staddon the same bar to wash with as she used to wash dishes and clothes. He points out: “There are dozens of products people use in the shower, each of which has a time debit.”

Cleaners’ verdict: Open verdict.
Environmental experts’ verdict: Whenever you like.

• This article was amended on 7 March 2019 because an earlier version was wrong to say that freeze-washing kills germs that can cause jeans to smell.