Be aware that for the first few minutes after turning off you will get the shower head leak a little. This is because the shower head has a large cavity inside that fills up with water in use. When you turn off, that water has to go somewhere, so it dribbles through the outlets of the shower head.
If both shower heads are off no water should be going to your shower head. the only thing it could be is your shower valve itself. you probably have a pinhole in one of your o rings on the valve stem. try replacing the valve stems.
I would start by replacing all the washers and o-rings on the hot and cold valves ( a lot cheaper than replacing the entire valve stem ).
Try replacing the Valves, and then the pipe holders, (for want of a better word) to the wall.
The shower diverter has a bad seal - very easy to replace.
If the faucet contains the re-direction valve (closes off the water from the faucet and redirects the water to the shower head) you need to rotate the faucet counter clock wise to unscrew it from the plumbing and replace it with a new one. Take the old one to your local box store and they can match it up for you.
No, the shower has both hot and cold water available.
have your heater core checked its probually leaking
they both distribute water
Flushing the toilet can affect the water temperature in the shower because both the toilet and the shower are connected to the same water supply system. When the toilet is flushed, it temporarily reduces the amount of water available for the shower, causing a drop in water pressure and potentially affecting the temperature of the water coming out of the shower.
That's the way they are designed. Most people do not want both at same time.
if it is lowering oil and water both and is not leaking it may have a blown head gasket and it is going out the tailpipe
Yes, yes they do reduce water consumption. Also, much like a filter for your tap water, it will help to offer cleaner water in the shower for both your water and hair.
Only hot water may be coming out of the shower because there could be an issue with the water heater, such as a malfunction or a setting that needs adjustment. It is recommended to check the water heater and its settings to ensure that both hot and cold water are being properly supplied to the shower.
Water continues to come out of the faucet when using the shower because the plumbing system in a house is designed to supply water to multiple outlets simultaneously. This means that water can flow to both the faucet and the shower at the same time without any interruption.
May be build up in the valve itself or the shower head.
There may have been some water left in the heater core when you disconnected both hoses at the firewall. I can't think of any other explanation since there is no water circulating through the heater core.