Everyday use of the Scientific Method

About a year ago I had an experience of how the scientific method could apply to a simple domestic situation. I thought I would share it as there are parallels between science and pseudoscience in this story of everyday folk.

I rented a house in Lincoln (UK) whilst I was an academic at the University’s School of Pharmacy. An electric immersion heater supplied hot water and that tank was kept full via a standard ball-cock valve on the cold water supply. All was not well with the hot water supply however, because there was a constant trickle of cold water into the tank irrespective of hot-water usage.


A lot of scientific discovery starts with pure curiosity, the “that’s interesting, I wonder what that is?” type question. A good example of this was when Richard Jorgensen became curious about patches of colour on petunia petals. His investigations led to the discovery of a whole new branch of genetics and won him the Nobel Prize in 2006.


Although I was not about to win a Nobel Prize, the constant trickle of water was nevertheless intriguing. I therefore formed a hypothesis that there was a leak somewhere in a hot water pipe. I traced all the pipework to see if I could find a telltale pool of water. There was none and hence no evidence for a leak.

Perhaps I was misinterpreting things and the constant trickle of water into the tank was normal. But the investigation at that point was superficial and so I investigated further. I found the main valve feeding the tank’s cold water supply and turned it off overnight. The next morning the tank was empty, so where had the water gone? I found the valve for the tank’s hot water outflow which I turned off and the constant trickle of inflowing cold water stopped. With both the cold water feed valve and hot water outflow valve off, the tank remained full. Clearly that constant trickle of water was not normal.

With no visible signs of a water leak, the tank was still emptying in a matter of hours. Perhaps the water was leaking somewhere I couldn’t see? I knew one hot water pipe went under the floor to feed the kitchen tap. It was a concrete floor and so I couldn’t get to the pipe to observe if there was a leak or not.

Make predictions from the hypothesis and test them

Scientists figure things out all the time without making direct observations. Instead they look at the consequences that a particular hypothesis might have and then work out what’s happening from there. In my case, there were no valves to isolate the under-floor pipes and so I had to get a little more inventive. The underfloor pipe branched off from the main pipe at a T-junction. One end of the T went to the kitchen tap (under the floor) the other went into the bathroom. So I came up with an idea that involved the flow of heat, rather than water.

The house had copper pipes which are good conductors of heat. By opening or closing the kitchen and bathroom taps, I followed the flow of water simply by feeling the heat running along the pipes. In technical terms, the heat was a surrogate for the water flow. With the bathroom and kitchen taps off there should be no flow of hot water and therefore all pipes should remain cold. Over time however, the pipe that went under the floor became warm, while other pipes remained cold. The conclusion was that there was a flow of hot water (detected from the heat of the pipe) under the floor, even when there should be none. The most likely explanation therefore, was that the pipe was leaking somewhere along its length under the floor.

Hypothesis becomes a theory

On the weight of evidence, there was a leak in the hot water pipe under the concrete kitchen floor. The evidence was consistent with the known laws of physics – for example, water flows downwards under gravity, copper conducts heat etc. In science, a theory has to be consistent with what is already known. For example, if some theory of biology breaks a law of physics, then the biological-theory cannot be right. Science is joined up in that way, each part has to fit with all the other parts. Pseudoscience on the other hand has no problem believing all the textbooks can be re-written just to accommodate their particular ideas. Getting back to my leaking pipe, it was time to call the landlord and get a plumber.

I explained my diagnosis to the plumber but he did not like the outcome. I could tell that the thought of having to uproot the floor did not appeal to him. He therefore said he would replace the ball-cock valve, which he claimed must be leaking, causing a constant trickle of water.

Counter hypothesis

I explained to the plumber how changing the ball-cock valve was not consistent with the evidence. How, for example, did the hot water tank empty when the ball-cock valve was isolated by turning off the main cold water tap? But he didn’t want to hear it. He told me he’d been a plumber for 20 years and so he knew what he was doing. An appeal to authority however, was not consistence with the actual evidence. The problem was that he didn’t want to accept where the evidence was leading simply because of the personal consequences to himself. Science frequently encounters such self-motivated objections. The economic consequences of reducing carbon dioxide emissions, for example, are so profound that the theory of climate change must be wrong!

Getting back to the reluctant plumber, after a little discussion, I got him thinking and he said he would check something out.

Independent testing of the theory

He went outside the house and dug down by the wall next to the kitchen. It didn’t take long before he hit mud. What he was hoping for was dry soil which would be counter-evidence for a water leak. In fact, dry soil under these circumstances would not have been particularly diagnostic one way or the other because the leaking water could have been flowing in any direction under the house. In science, some evidence is robust and other evidence is more circumstantial. It’s a common fallacy to confuse the two as being equal. The wet ground in this case, was supporting evidence for the leak-theory but the plumber then rationalised the mud by saying it had been a wet year and it could just be ground water.

Unsinkable rubber duck!

This is a term used by rational thinkers when someone finds a way round every item of evidence presented to them to support their own preconceived position. Young earth creationists who believe the earth is less than 10,000 years old are masters of the unsinkable rubber duck. Point out that light from distant stars has taken many millions of years to reach the earth, then they will claim the speed of light has not always been what it is today. Likewise, no matter what the outcome from the plumber’s test-dig by the kitchen wall, it would reinforce his own viewpoint or at least not change it. But I had to be careful because although the mud seemed to support my leak theory, the possibility that is was a coincidental ground water could not be ruled out as there could have been multiple reasons for this observation. Scientifically, I could have added a tracer dye to the hot water to see if it ended up in the mud. Even for me however, this seemed a little over-the-top and so instead, I suggested that he dig another test hole around the other side of the house to see if that was wet due to the water table. He thought about it but declined. To him, unwillingness to further test his theory seemed to reinforce his own position.

Confirmation of the theory. In science my water leak would have been tested in a multitude of ways. Someone may have come up with some new ingenious methods and others would have confirmed or failed to reproduce my data. Then those tests repeated and so on, with the results either reinforcing the theory, leading to modifications of the theory or even to discard it and start again. Pseudoscientists on the other hand are content to accept the first whiff of flimsy evidence that might vaguely support their point of view and ignore far more robust evidence against them. The case of my hot water was a little more domestic and anyway, showering at work was getting tedious.

So what happened? The plumber and I did not pass on particularly good terms. I got on well with the landlord and so he let me find another plumber for a second opinion. The second plumber wasn’t that bothered about my method of diagnosis as he saw a simple solution. He simply put in a new pipe above floor level, bypassing the one with the leak. He took about an hour and afterwards the problem was solved. The constant trickle of water to the tank stopped.

In science, this would have opened other questions such as, exactly where was the leak and what was the cause? Even without knowing this level of detail however, the theory of an underfloor leak in a hot water pipe still stood firm. In contrast, pseudoscience often presents any gap in knowledge as evidence that the whole theory is wrong. You don’t know exactly where the pipe was leaking, therefore that was not the cause. You can’t observe every intermediate species between Hypohippus and the modern horse, so evolutionary biology must be wrong. Or the gap is filled with any old nonsense; aliens living under my house were stealing the water – that type of thing. Well, you can’t disprove it, can you?

And just a final note. My persistence with the first plumber was not about being right, it was about the evidence. All too often there are those who evoke the name of science to prove themselves right at any cost. Science is the exact opposite of this. Regarding the first plumber, if he could find better evidence to support a different theory then I would have been very pleased to change my point of view. Even if an alien had suddenly appeared out of the test-hole!

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