We just bought a house and have noticed while taking a shower, the water will alternate between hot and cold the entire time. Anyone know what the cause of this could be? I'm hoping it's a simple fix so we can avoid paying for a plumber.

We just bought a house and have noticed while taking a shower, the water will alternate between hot and cold the entire time. Anyone know what the cause of this could be? I'm hoping it's a simple fix so we can avoid paying for a plumber.

What kind of Water Heater??

We just bought a house and have noticed while taking a shower, the water will alternate between hot and cold the entire time. Anyone know what the cause of this could be? I'm hoping it's a simple fix so we can avoid paying for a plumber.

Are you on a well? If so it is most likely the pump kicking on and off. If it happens every minute or so you need to look at the pressure tank.

We just bought a house and have noticed while taking a shower, the water will alternate between hot and cold the entire time.



any number of things ........ how old is the house / shower faucet

1. loose washer on one of the shower stems, it old enough to have flat washers
2. you have a bad solenoid valve on the washing machine, allowing water to pass from one side to the other ........
3. low flow, so when a toilet is flushed somewhere else in the house, caused a drop in pressure /flow in hot water - causing the shower to go cold ....
4. cold water input in the tank is rotted off, so instead of the cold water entering the HW at the bottom [the closest to the fire] and exiting the top .... cold water can take a short trip across the top of the tank to the exit.
5. bottom heating element is no longer heating ..........

Possible bad anti-scald valve in the shower diverter. Not all that uncommon.

Happens a lot if you have a oil hot water boiler system. You can minimize the hot/cold swing by turning down the 'volume' of your water, ie, slow down the flow of the water, don't turn on the shower full blast. The boiler can keep up more easily.

2. you have a bad solenoid valve on the washing machine, allowing water to pass from one side to the other ........Showering in the washing machine is just plain wrong!

You could narrow this down a bit by checking if it happens with "just" hot water on, does it happen at the sink as well, just in the shower in question?????????

Thanks for all the suggestions. We are on a well, and I'm not sure what kind of water heater it is. I will post that once I look at it. The water will go from being warm, to extremely hot or cold, to the complete opposite. Then it will even out, only to do it a few minutes later during the shower. It only happens while in the showers, and not at the sinks.

The house is 26 years old.

What kind of Water Heater??

It is an AO Smith glass lined water heater.

It is an AO Smith glass lined water heater.

Going to assume electric, not too many gas fired water heaters around here.

And on that, ignore my comment about a boiler.

You sure no one is turning water on and off, dishwasher, flushing, etc, while you're showering?

Thanks for all the suggestions. We are on a well, and I'm not sure what kind of water heater it is. I will post that once I look at it. The water will go from being warm, to extremely hot or cold, to the complete opposite. Then it will even out, only to do it a few minutes later during the shower. It only happens while in the showers, and not at the sinks.

The house is 26 years old.

I'm GUESSING it's your shower hardware..

At least that's where I'd start the house demo at..


If not, we have a slightly used 80 gallon electric water heater that we'd let you buy for say a Brazillion dollars.. (negotiable).

Going to assume electric, not too many gas fired water heaters around here.

And on that, ignore my comment about a boiler.

You sure no one is turning water on and off, dishwasher, flushing, etc, while you're showering?

Yep, electric. There is no other water source in use while showering.

I'm GUESSING it's your shower hardware..

At least that's where I'd start the house demo at..


If not, we have a slightly used 80 gallon electric water heater that we'd let you buy for say a Brazillion dollars.. (negotiable).

Thanks for the tip. I will talk to the hubby and see what he says about the water heater. Ours is currently a 40 gallon.