We have a well system, and are experiencing occasional hot water temp spikes in the shower, which seem to occur at/near the end of the well pressurizing cycle. The system is not "short-cycling." We have a standard shower valve system - not pressure-regulating. No one is running any other water when these spikes occur. They don't seem to occur every time. Yesterday it happened on 2 of 4 pressure cycles. My wife ran her shower at less than full volume and claimed she had no spike occur.

What could be the cause of these HOT spikes?

Specifically how long has this been happening, and have you made any changes or repairs to the system?

No doubt, you have a hot water mixing valve out of the furnace or tank. Could be the age of the valve along with the fluxation of the water pressure.

Do you have a thermostatic mixing valve at water heater?

Where your water heater and shower?

talaniman - for the past week or so and not before. No we have not made any changes or mods to the system.catonsville - no mixing valve until you get to the main shower control (Moen).macplumb - no mixing valve at the water heater. Water heater is electric, under the kitchen counter. Home is a small A-frame. Shower is only on the other side of the wall, in the bathroom. Feel free to ask any other questions or request a diagram of the plumbing.

Quite simply. The problem is occurring from lack of a pressure balanced shower valve. As well as a drop in cold water pressure. The question is why the cold side is the only thing affected. Perhaps the proximity of the water heater and head pressure along with thermal expansion are the issue.

How big is your water heater?
Mac

Quite simply. The problem is occurring from lack of a pressure balanced shower valve. As well as a drop in cold water pressure. The question is why the cold side is the only thing affected. Perhaps the proximity of the water heater and head pressure along with thermal expansion are the issue.

How big is your water heater?
Mac

EXCEPT: this problem has not occurred until recently, and we've been here almost a year. So, why now? What has changed in the system? Water heater is only a few feet from the shower control. Heater is small, maybe 20 gal. Sits under the kitchen counter. I took a shower yesterday and the well system went through 4 pressurizing cycles. The HOT spike only occurred on two of the 4 cycles, always near the end of the pressure cycle. My wife took a shower today, saying that she didn't have the control on full volume, and didn't experience any spikes.

Well Pump Short Cycling: What Causes "Water Pump Short Cycling" - a water pump turning on and off too rapidly - How to diagnose water pump short cycling and how to restore lost air in a building water pressure tank - private pump and well system do-i (http://inspectapedia.com/water/ShortCycleCause.htm)

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