Why does water pressure in the showers changes when temperature changes?
In: Engineering
Your water is coming from two pipes, one hot and one cold. When the water is cold, you’re only getting water from the cold pipe. When the water is hot, you’re only getting water from the hot pipe. But when the water is warm, you’re getting water from both the hot pipe and the cold pipe at the same time, which is why there’s more pressure.
Hi, I am a plumber of over 4 years. Basically there are tons of different types of valves and they all act differently. Since you are specifically asking about a shower, those valves have a point where the hot and cold water meet (mixing valve). The pressure of the water doesn’t change. On older shower valves there if nothing to prevent the hot water to flow into the cold water side of the valve or vice versa. This is where the problem is for example if someone were to flush a toilet close to the shower it would feel like there’s less cold water pressure but the hot water is actually backfeeding into the cold water line. Or if someone turned on only the hot water to wash their hands at that bathrooms sink the water in the shower may feel colder or “less pressure” but it’s the cold water backfeeding into the hot water line. On newer shower valves, kitchen faucets, etc (especially single handled valves) there is a part called a pressure balancing spool. This is similar to a backflow device or a check valve where it will only let water flow in one direction. This eliminates the effect of “less water pressure”. . .
Edit:
And now that I’m reading your question again for the third time I’m realizing I read it wrong and gave you the wrong answer as well as a bunch of useless information. Instead I should have asked what you meant by temperature changes. Do you mean weather or temperature in the house?
The water pressure is being generated either by the city water pumps or your home well pump. But the pressure felt at the outlet of the pump is not what is felt at the faucet; with every inch of pipe it flows through, every pipe bend, etc., it reduces somewhat. This is sometimes referred to as “pressure drop” or “head loss”. The cold water in your home flows directly from the well pump or city supply connection at your house. The hot water, on the other hand, flows first through your water heater; this incurs greater head loss, since it’s a longer and more tortuous flowpath. So your hot water at the tap has a somewhat lower pressure. Consequently, when you adjust temperature, you also adjust pressure.
This depends heavily on the country you’re in. Many countries have separate lines for hot and cold water. At least where I live the hot water has less pressure so the hotter you turn the water, the less pressure it’ll have.
Though I don’t know if this is a safety feature or just because of the way the water is heated.
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