3way switch

The upper red tap is hot water from the tank, covering heating.

 

yes - and it's a valve not a switch - and it looks like you have another isolation tap (without it's red wheel) lower down near the pump

 

Not wishing to be a scaremonger, but 'gate' valves such as those are prone to either seizing or the shaft snapping when you really need to use them, especially if they haven't been operated for a while, I'm sure others on here will have had the same problem in the past tbh.

 

The gate valves are the ones with the red handles, isolation valves, the ones that you need to be able to turn off to isolate pipework in an emergency of for remedial works to the pump and three port valve-obviously if those have seized.....

 

The red valves are hot water for heating.

To isolate the incoming cold water to the cylinder there should be a valve that looks a bit like a door handle on a pipe about half up the cylinder that goes into the bottom of the cylinder coming from the loft.

To totally isolate the water supply there should be a main stopcock under the kitchen sink, sometimes they are elsewhere but most of the time under the sink.

 

Looking at those photos It appears that the pump valve has leaked nothing to do with the 3 port valve. those gate valve that you have fitted are unusual but appear to have been installed to allow the replacement of the 3 port without draining down, which is not common practice but won't affect your system unless you start closing them. However to fix your minor problem you all you need to do is to get yourself a 22mm pump valve (get the gate valve type and not the ball valve type). Then you will need to partially drain your system remove the offending valve clean the threads on the pump if you can get on a new rubber washer rathe than the fibre ones supplied with the valves. Re assemble, refill add inhibitor job done about an hours work

 

No thats the isolation to your cold riser to the tanks in the loft. what you have on your heating system is two 22mm gate valves which is not the norm but is not an issue provided you don't turn them off. Someone at some time has decided to fit them so that the 3 port valve can be changed without draining down. These valves are not necessary as most professionals bung the system to replace the valve if needed. From your pictures it appears that a pump valve has weeped, causing the build up of crud on the pump. This alone is not an issue unless you can feel wet on the pump when its either hot or cold. Otherwise you have no issues that should cause you to loose sleep. Hope that helps.
Dave

 

There is no particular isolation tap for central heating if it leaks turn off the cold main riser or tie up the ballcock and drain the system. but worrying about the system leaking is a bit like worrying if your cars going to break down.