Air in pipes

Hey Rock,

1- How can I take the air out from the hot water pipes.
Summary:
I bought a house and the plumbing was re-done just before and also a new gas hot water tank was installed. Sometimes the noise scares my kids.

It's not air that makes the sound, it's "water hammer". It's water pressure hitting a elbo when you close a faucet. Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is importent.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill.

2- Why do we have a hard time to have a shower with luke warm water?
We can't adjust it it's either gets too hot or too cold.
Was there suppose to be a regulator or something set up?

You don't give me anything to go on. Brand name and type of faucet, (one handle or two knobs?) How old? Is the hot water pressure Ok? Is the hot water pressure Ok in the other bath fixtures? T'm going to assume that you have a one handle faucet. Unless you have a "temptrol" that controls your faucet the cartridge controls the hot and cold mix. Before I can be more specific I'll need all the information you have including the model # if you have it. Regards, tom