Can I replace the valve on this water hammer arrestor?

Transfer Valve plumbing first thoughts

All the connections bothers me. Should it?

What would cause this?

I turned the kitchen faucet on and the water came out like this. I tried the bathroom and it was clear. Then, I ran the kitchen faucet a bit longer and it eventually came out clear. So what is up plumbing?

How can I stop loud banging of waste water pipe?

In my bedroom I have this large waste water pipe that spans the length of the wall. Whenever folk in the flat or below us use water it causes the pipe to give this loud continuous banging. V annoying and hard to sleep through. Landlord sent contractors who cut this hole in the dry wall (level to head) and attached the pipe. This helped for the first week no noise but it quickly came much further up the wall above the hole where I can’t reach. Is there anything I can do to prevent this happening?

Has anybody used these or even heard of these before?

Straub coupling, apparently it's good for 26 bar, which equals 377 psi!? I use them on blown out pvc water mains when we can't wait for glue to cure. Lots of pvc mains here in SoCal

What needs to be done

Need help from someone that is in a little more in the know than I am with this. What am I looking at here and how urgent of a fix. This is a pipe above my water heater from the house we just bought. Thanks!

Clogging Issue

My roommate has clogged the toilet twice in the past 3 days needing a maintenance person to fix it and says that our toilet paper is to blame for it. I don't know anything about how well toilet paper dissolves but could this type cause that severe of an issue? Thanks in advance.

Is there an easy way to change this?

Im looking to set up a timer for a sprinkler in my yard, and was wondering if it would be possible to change this as it is very old and gets stuck sometimes. Possibly to a ball valve?

Slow drip

My plumber left with this slow drip, is it a big problem to fix?

No water after opening valve

My kitchen sink was the only place in the house with low pressure, even after installing a new faucet. I followed a recommendation I saw in another thread to remove the inlet valve and flush the pipe out in case sediment had built up behind the valve over the years. I also installed a new valve. After turning the water back on and opening the valve, there’s zero water to the faucet (or attached dishwasher). Water’s restored elsewhere in the house. I feel like I’m missing something embarrassingly obvious but even after redoing the valve install there’s still no water to the faucet.

Can someone give me advice on how to stop this from a bath waste. Please…. Solvent has not yet been applied