How do I repair/replace the hot faucet?

Newer faucets are made to save water by having restrictors in them. Some can be removed, some can't. Phone the maker.

There should be a valve on the outlet and inlet side of the water heater. Make sure they are fully open.

If you will make contact with George at M-One-Specialites he can track that down for you and help you get that fixed.
He has a very extensive list of repair parts for faucets and knowledge of how these work.


Rod
US Parts Center

You reinstalled the cartridge in the wrong position.you need to get parts break down from kohler web site and reinstall properly.

Depending on what brand of faucet you have you may need to replace the cartridge,moen and clones, or stem/cartridge on delta and similar. I would not replace the faucet until I was sure that you had hot water to the kitchen faucet and the faucet was going to cost more to repair then replace.
If you have supply valves for kitchen faucet I would shut them off and try to take faucet apart to determine where the hot water is stopping. Do not try to force things to much or you may make the faucet totally useless.
If you know what name brand your faucet is you can find several sites on u-tube that show good repair procedures.
I hope this helps you. Thank you.

remove the device from faucet and look into it for a small screen is it clean.

The problem is that when you disturb the galv. pipes, the gunk inside breaks loose, and travels to the faucets, gets stuck, and limits the volume of water that comes out.
If possible open the lines at the service valves, and force water through the spigot to fluch out the faucet. The service value could also be partially clogged, keep that in mind

Do you have your own hot water tank? or is there one serving many units? There is a 'dip tube' in hot water tanks, if it gets old it sometimes deteriorates and small parts of plastic get loose and will float around in the tank, if a piece finds it way up to the outlet then that might explain why you are getting the low water pressure. one wat to check is to twist off the aerotor on the end of your faucet, if there are any small pieces of white plastic then you will have to replace the dip tube and maybe even flush out the tank. it is also possible that a piece of plastic has traveled up the water line and it stuck in the faucet cartridge.

you will need a puller more then likely but what you can try is a little wd-40 lubricating spray

It could be one of two problems, one simple, one serious.

• Easy fix
  

1. Turn off hot water angle stop under sink to faucet.
2. Remove supply line from hot angle stop.
3. Place end of supply line in a small bucket to catch some water.
4. Turn on cold water for a couple of seconds and backflush debris from faucet.
5. Reconnect supply line.
6. Turn on angle stop and test
   

• Complex fix

If you have steel pipes you may be experiencing reduced flow due to corrosion in your pipes. Reduced hot water pressure in the kitchen faucet is usually the first sign since this is the faucet that is most used in the home.

Repiping is a job for a professional. Another symptom you may need a repipe is orange colored or rusty water.