Water pressure goes... up?

[swimmer_spe]

I have been posting my water woes, but I have a new one....

Wife decides to take a shower while the washer is going. The hot water pressure goes... UP....

I have been having an issue with low water pressure, especially on the hot water side. Why would the pressure go up?

We are on lake water, not city water.

 

[Tyler S]

Do you have an electric hot water heater?

 

[swimmer_spe]

Do you have an electric hot water heater?

Yup. It's about 8 years old.