Help identifying valve function

[alexis.chu]

Hello and happy Easter! Would anyone be able to explain, from the photos and the video of my HW tank, what do the 2 red valves control and whether they should be closed or open? Upper one is sitting below an intersection below the CH pump. I wonder if, when opened, this contaminates the water in the HW tank with the water used in the CH system? Lower one seems to be cold supply.

Little bit of context: trying to cut off water coming into the HW tank. Gravity system (UK), got a cold water tank in the loft and the HW tank in the airing cupboard.

Thank you in advance.

Photos below, video here: https://drive.google.com/file/d/19pp5Y0LjUhGxqvuGmtVMVREkmZeTAisi/view?usp=drive_link

 

[denso13]

Look like they are a bypass and for restricting the coil return. If it is all working ok just leave them as they are, they aren't contaminating anything, the water in the cylinder is a separate thing.

 

[Alec_t]

If you trace the pipe coming down from the loft tank to the cold tank, hopefully that will have a stop/service tap in it. If not, you could put a bung in the loft tank exit, or shut off the feed to the loft tank and drain it.

 

[alexischu]

If you trace the pipe coming down from the loft tank to the cold tank, hopefully that will have a stop/service tap in it. If not, you could put a bung in the loft tank exit, or shut off the feed to the loft tank and drain it.

Thanks, yeah I think I'll drain everything like I did last time.

But what about these 2 red valves? I fiddled and closed them (stupidly) thinking it'd prevent the tank from filling, and I'm doubting if the top one was already closed or not ... So that's why I'd like to understand their purpose.

 

[denso13]

what about these 2 red valves? I fiddled and closed them (stupidly) thinking it'd prevent the tank from filling, and I'm doubting if the top one was already closed or not ... So that's why I'd like to understand their purpose.

As above, the top one is a bypass and should be cracked open, the other is to throttle the cylinder coil return, open roughly half way.

How much they are open/closed isn't usually critical.

The feed from the loft cistern should be on the opposite side of the cylinder

 

[Harry Bloomfield]

But what about these 2 red valves? I fiddled and closed them (stupidly) thinking it'd prevent the tank from filling, and I'm doubting if the top one was already closed or not ... So that's why I'd like to understand their purpose.

Looking directly at the red wheel handle - clockwise to close. Gate valves may not close completely.