I have a 740003pc the cold tap wont stop running

This important part is right at the end, you have a well!! It sounds like you may have run it dry? Check the well and the pump first. The rest is stop valves and pipes to the tank and beyond and not likely to be causing issues. Your sediment issues and problems with the anode is also due to using well water which is nearly always loaded with minerals..

Bleed your propane system by running the stove for a sec. if that doesn't work go out to the heater and listen for the ignitor clicks see if it's trying to lite. My fifth wheel does this first time every season.

assuming you have checked the washer of the tap in question as they act like reeds in a wind instrument when they start to perish?Otherwise it may be trapped air in pipes.one possible solution is to open the tap slightly then using a cloth try to stop the water flowing out by finger/hand pressure and release and restrict several times over a period of a minute. , due to the principle that you can not compress water only air the air now has a chance to escape.try this on all the taps in the system from top of house down.also bleed any radiators you may have before any if the above.Some may suggest connecting the cold supply into the hot via hose and turn on the taps ever so slightly a quarter of turn to force air back into tank as cold supply is usually higher pressure that the gravity fed hot supply.

Check for water leak.
Turn off all taps and put ear against pipe
Make sure toilet or outside faucet are not connected to hot line.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Gene

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check hot water pressure valve

You can find the instructions here....

http://globalimageserver.com/fetchDocument.aspx?id=f43430fe-a847-4371-b6c7-cab5eb0e34a6

from a plumber all hot and cold connections on all major showers are hot on the left and cold on the right just like the taps on your sink or washbowl

you need to change the cartridge, it is a temp control and is going bad so it keeps you from burning yourself it is like a mixing valve and is givng more cold water, that way you don;t get burned,,

your pipes are clogged, what if you were to not turn on the cold and turn on the hot does any water come out at all, with just the hot side turned on,, if not there could be a valve that has been turned off, or the pipes are clogged

there is a little cap on the hot and cold side above the shut off valves, turn the water off at these valve and take the caps off there are filters in there clean them off and reinstall them that should take care of the problem, you might want to flush the tank while your at it hook a hose to the hot side connector and run it out side or to a sump pump then turn on the cold water and flush it out you can also reverse this procedure by doing it on the cold side