I know little about plumbing.
I noticed couple times over past few months - got hot water from cold water faucet for a few minutes, then it went away.
Now, regularly first thing in morning or when water faucets sit idle, hot through cold faucets for several minutes AND cold from hot faucets sometimes.
- not a single faucet or shower, but all faucets affected
- house is 2 1/2 baths + kitchen sink (with dishwasher attached) + additional sink
- especially occurs 1st thing in morning or after no water running for a few hours
- oil furnace (forced air) with separate oil water heater
- appears to have been gradual change, now every day
- sometimes a few minutes and sometimes >10 minutes (I can take a comfortable hot shower with faucet set all the way to cold)
- after speaking with plumber, who spoke of scald guard in shower faucets and possibility that hot water (more pressure) was pushing through the guard and backing up into cold water side then entire system (showers are each single knob faucets) suggested that we set shower faucets all the way to cold when not showering, but issue still happening

Looking for ideas on what could be cause... thanks in advance for your help

Please tell us the bran and the model number of your shower faucet, Thanks.

John