Michael Phelps
US Olympic swimmer Michael Phelps (Reuters)

Michael Phelps, Ryan Lochte and all those who champion peeing in the swimming pool can take a deep sigh of relief after scientists said there was nothing wrong with the practice.

Experts from charity organisation Sense About Science (SAS) confirmed what the world's most successful Olympian said over the London 2012 Games: peeing in the pool "is not bad".

"Everybody pees in the pool. It's a normal thing to do for swimmers. When we're in the water for two hours, we don't really get out to pee. Chlorine kills it so it's not bad," Phelps, 27, told the Wall Street Journal after his teammate Lochte, 28, revealed that he relieved his bladder as soon as he entered the water.

SAS, which every year challenges and examines scientific claims made by celebrities to prevent inaccurate information gaining public acceptance, upheld Phelps' assertion - with some amendments.

"In fact, Michael, urine is essentially sterile so there isn't actually anything to kill in the first place," biochemist Stuart Jones wrote in SAS' Celebrity and Science 2012 review.

"Urine is largely just salts and water with moderate amounts of protein and DNA breakdown products. Chlorine just prevents bacteria from growing in the pool.

"So you're basically right - peeing in a swimming pool, even if all swimmers do it simultaneously, has very little impact on the composition of the pool water itself. An Olympic-size pool contains over two million litres of water and a single urination is somewhere in the region of 0.2 litres."

"To have any significant effect on the overall composition of the pool water you'd need a serious amount of peeing," concluded Jones.

But SAS was harsher with other celebrity claims.  

"There really isn't any evidence that anyone can 'heal' your house, Simon," psychologist Richard Wiseman told Simon Cowell, who had tweeted that a healer had brought "good energy" to his Beverly Hills mansion.

"Normally, house healers say a few prayers and occasionally explain how rearranging things will help the energy flow through your property. This might make you feel less anxious and so feel better, but it's a lot of money to pay for a placebo and a bit of furniture shifting," Wiseman said.

US Republican primary candidate Rick Santorum got similar treatment for his belief in creationism.

"If he [Utah governor Jon Huntsman] wants to believe he is the descendant of a monkey then he has the right to believe that but I disagree with him on this liberal belief," Santorum said early on 2012.

"Rick, you seem to be confusing the way in which scientific knowledge is acquired with a particular political belief," replied biologist Stuart West.