The kitchen is probably closest to the water heater and the shower is the farthest. Water cools down the farther it travels through the pipes.
Stoppage
The plaming tubes are all conected.When the cold water run in kitchen the cold water at the shower become less,so with less cold water at the mix cold-hot (the balance is desterb),making the water hoter.Same if you turn on the hot in the kitchen the water will be colder in the shower.
Maybe the kitchen is further away and on smaller pipe.
Well, if you take a shower with hot water, it should get worse, since a hotter temperature increases blood pressure....
Have a temperature / pressure balence type installed
The hotter the water you use w/ the bleach, the less effective the bleach may be. I'd use it w/ water no hotter the what you would use to bath/shower in.
Yes.
your vent on your shower or kitchen (if you have one) is not working and either the air from the water in the shower drain is carried down stream till it T's off to your kitchen sink then the air follows to your kitchen sink drain line backwards and to your kitchen sink trap and then bubbles through your trap because your water in your kitchen trap can not drain but the air has enough pressure to go through it OR your water from your shower is flowing past your kitchen drain T and making a siphon which causes air to go through your kitchen trap and makes the gurgling sound one way to fix the problem is to add a Vent line on your kitchen drain and your shower drain with in 42" on 1 1/2 or 60" on 2" on your trap arm if you want to follow the UPC code. Note to above Respondent: That little dot next to the question mark is a "period". Try throwing one in once in a while.
Yes, remove your old shower valve and fit a new Moen anti-scald valve. This will not change when other items are turned on.
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the temperature is hotter and one is cooler.
It is bad overall to be dehydrated, but it really depends how hot your showers are. The hotter the more you will sweat, which means the more water you lose in your body, some cases people have passed out in the shower because of this.