Without knowing what you are trying to do, advice is tricky, but it seems that you have not switched the mains off. In the UK it would be illegal, but there is a slim chance that the cold tap is not connected to the rising main, in which case, that explains the flow, and the tank must be drained
You can test the water for chlorine levels using a pool water test kit. Mains water typically contains chlorine, which is used to disinfect the water. If the water shows a chlorine residual, it is likely mains water.
see a plumber
There may be no hot water coming out of the kitchen sink due to a problem with the water heater, a blockage in the hot water pipe, or a malfunctioning faucet. It is important to check these potential issues to determine the cause of the problem.
To drain the water that is in the pipe or spout..
A water faucet is the mechanical device fitted to the water supply pipes over bathroom and kitchen sinks. When turned on they supply water.
If you assume that the water entering your house in the mains pipe is at a constant pressure (this is a relatively good assumption) then the more outlets you give for it to flow from, the lower the flow rate from each one. Say you are supplied 1 litre per second and your shower is using all of this. Now, turn a tap on to 0.3 litres per second and there is 0.7 litres per second coming from the shower head. Showers are often upstairs and kitchens downstairs, so if the tap in question is in the kitchen then the effect will be greater than if they were both on level. The pressure of the water in the kitchen tap is made larger by the head of water pushing down from upstairs, and when both are turned on, the kitchen tap can "steal" more of the shower's water than a bathroom tap would when twisted the same amount.
If it's coming from the roof then the bathroom ceiling will have a water stain on it too. If you don't see this then it is coming from your bathroom.
I just brought a Glacier Bay pull down ceramic kitchen faucet Model 896408. After installing it, the cold water wasn't coming out of the faucet. It turned out the problem was the coldwater supply line inside the faucet was bent & twisted. As a result, when the body of the faucet was attached, it had to be turned just a little to position it correctly, this tighted and choked the water supply line even more- which meant "no cold water." Waiting on replacement line from Glacier Bay, which, I am certain, will correct the problem.
In urban areas, the water is pumped through water mains called force mains (large delivery pipes) and up into a water tower (also know as a constant head tank). The force of gravity then helps to send the water through street mains and secondary mains to homes, businesses, and institutions.
The mains water has probably been turned off and turning on the tub has drained the tank.
Yes, remove your old shower valve and fit a new Moen anti-scald valve. This will not change when other items are turned on.
There may be no water coming out of the tap when it is turned on due to a possible issue with the water supply, a blockage in the pipes, a malfunctioning faucet, or a problem with the plumbing system. It is recommended to check for any visible blockages or leaks and contact a plumber if needed to diagnose and fix the issue.