why does the water in the shower get hot when a toilet is flushed?

Question

its one of those things that kinda makes ya wonder

Answer 1

All the house's hot water is supplied from a pipe leading from the hot water heater.
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All the house's cold water comes directly from a pipe leading from the house main.
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From the water main the pipe splits with one branch going to the water heater to be made hot, and the other branch going to the cold side of all faucets and to all toilets through further branching.
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When the pipes split, so too does the water pressure. If the water pressure at the house main pipe is 100 psi(pounds per square inch) then the split to the water heater and cold supply side will be 100 psi for each of those two branches as long as neither branch is opened.
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If a house has one kitchen with one faucet, one bathroom sink faucet, one bathtub/shower faucet, one toilet, washing machine faucets, and one outside faucet for the garden hose, then that house will have 4 hot water outlets and 6 cold water outlets.
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From the hot water side of the water heater the pipe will split to just 4 outlets for hot water each with the potential for 100 psi at each outlet; while the cold side will split to 6 outlets each with the potential for 100 psi. (with all outlets open at the same time each would express 10 psi)
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When the shower is on and the hot/cold faucets are evenly opened to make the shower temp. comfortable for the user, the pressure for the hot is 50 psi and the pressure for the cold is 50 psi. When the toilet is flushed the pressure for the hot is 50 psi and the pressure for the cold is split between the shower and the toilet to about 25 psi each.
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The cold side pressure could be more or less than 25 psi at the shower depending on amount of water used by the toilet, size differences of the supply pipes, age and type of pipes and the like. But, even at the ideal 25 psi reduction, the shower would feel markedly hotter as there would be less cold water touching the showerer.

Answer 2

When the water flushes from the toilet, more water has to come in the pipe to fill the tank. In most bathrooms, the pipe that brings water into the toilet tank is the same one that brings water to the bath/shower.

That's not a big deal when the toilet tank is the only thing receiving water. But if the shower is running, there is a constant flow of water into the bathroom thru that pipe. If the cold water pressure is not decreased, when the water pressure increases to fill the toilet tank, there would be a huge gush of cold water into the shower because that part of the pipe is open.

The best solution is not to flush the toilet while someone is showering. Of course, if you're not gonna flush...don't use the toilet till the shower is done!

Answer 3

The piping that goes to the shower commonly has a connection going to the toilet. Whent he toilet flushes then the cold water is shot in that direction making there be more hot water coming out of the shower.

Answer 4

Because the toilet uses cold water. When you flush the toilet and shower is running, a lot of cold water is used to flush and refill the toilet. So you end up with less cold water going to the shower, which makes the water hotter.

Answer 5

Because the toilet pulls all of the cold water to it leaving just hot water in the shower.

Answer 6

Because the water to the toilet is hooked up to the cold water line and pulls the cold to the toilet, taking the cold going to the shower away from it.

There is fix for that.... Can ask at Home Depot or Lowes...

Answer 7

Don't flush toilet when someone is showering or install 'scald proof" faucets in bath & sink like we did.

Toilets are hooked up to only cold water lines and it will rob some of the tub and/or sink cold water so it can refill tank = less cold water in tub & BR sink area = hotter water.

Answer 8

YOUR WATER FEEDING THE TOILET IS FED FRO MTHE MAIN SUPPLY, WHEN THE TOILET GET FLUSHED, AND THE SHOWER IS RUNNING IT SUCK A LOT OF WATER FRO M THE SHOWER ,SO LESS COLD WATER IS FED TO THE SHOWER ,, YOU NEED TO INSTALL A RES VERE PRESSURE VALVE

Answer 9

the toilet takes the cold water
thats coming from the shower

Answer 10

the toilet hogs the water coming into the house.... which means you get blistered.