Is there a way to connect 1/2 inch copper plumbing pipe to 3/4 inch pex lines? Is there a special connector that can be purchased for such a retrofit?

If you tried using a typical 1/2 to 3/8 faucet connector such as https://www.homedepot.com/p/3-8-in-Compression-x-1-2-in-FIP-x-20-in-Braided-Polymer-Faucet-Connector-B1-20A-F/100459572, and it didn't work then ignore this answer, else...

Plumbing pipe size can be misleading due to the fact the pipe diameter is based on outer diameter and the inner diameter varies with wall thickness. To determine standard pipe diameter you measure the outer diameter and subtract 1/8".

The typical 1/2 inch pipe has an outer diameter of 5/8" and like wise a a 1/4" inner diameter pipe is a 3/8". So likely the typical faucet connector is correct. But you may have something unusual so FYI.

I know of no reason why you shouldn't use a pex adaptor or any suitable reducer.

Water pipes in RV are Pex, which is not the same as PVC. Pex will freeze, but is designed to not burst when frozen. If you have located the broken pipe, it is simple to replace. Using a PVC cutter (looks like cheap shears) cut out the broken piece. Most likely the pipe size will be 1/2 inch. Pex comes in three different colors: white, red, and blue. Most likely the RV pipe will be white, but the color does not matter as the pipe is of the same material. Pex can be bought at stores like Home Depot, Lowes, or other hardware stores. The connector fittings can be bought at the same stores. The simplest to use fittings are the push-on self sealing fittings. There are cheaper fittings, but they take special tools to install them. The estimated cost of a 2 foot distance pipe repair is about $10 to $15. The time required depends on how difficult it is to "get to" the broken pipe.

I wouldn't put psi any higher and it should run two small homes

use pipe cutter to lop off end and sand the last 2-3 inches down with abrasive sand cloth. if you never braised before, i would recomend sharkbite plumbing fittings. comes in 1/2", which is what it looks like you have. it slides onto existing pipe (copper, pvc, cpvc and pex) and makes a seal, while the teeth inside keep it from coming off. there is a ring on the end that you can push in with a specific tool (which comes with some fittings) to remove it. they have extentions, valves, couplings and terminations in sharkbite. they sell them at any home depot. good luck and have fun

Sorry to read about your problem, I hope this helps you out.

you must have a large amount of solder resin in your line, thats from putting the joints together on your copper pipe...should have put pex pipe in...may have to run a resin cleaner thru the lines

I tried to help you. Please help me and Rate/Vote on my response, thanks and good luck

Your plumber is correct your unit should be plumbed with cold water.
Easy fix if you need to do it yourself.
More than likely they have a 1/4 inch line taped into a 1/2 inch copper line near your furnace.
Simply shut off the tap on the undesired line and disconnect the 1/4 inch line.
Install a new tap on the cold water side and reintall supply line to the unit.

Do not remove the old tap on the hot water line simply shut it off because it puctures the line, hence the tap.

They do make a compression coupling for galvanized pipe, but I don't trust them very much. When you unscrew the joint with a pipe wrench just make sure to back it up with another, so you don't start to unscrew the next joint back.

if you don't know how to sweat copper the best way is cut out the split,and replace with compression couplings and the rite size and length of copper. or you can use sharkbite couplings and pex pipe or copper. sharkbite is the easiest way to go,you just push them together. home depo or lowes carry both

To get the water to the dishwasher, it depends on your plumbing setup. If you have shutoffs under your sink(1/2" X 3/8" compression angle stop), you will need to buy a 1/2" x 3/8" compression double stop. This will be easy to change.

#1 Drill a 1 1/2" hole in the back bottom of the cabinet to run your water, drain line, and power cord through.
#2 First turn off the water at the Hot Water Tank, or the House supply, and turn on the sink to relieve the pressure.
#3 Next remove the Hot supply stop, and install the double stop.( The nut and ferrul do not have to be removed, as they will attach to the double stop. Reinstall the hot supply to the sink to one of the connections on the double stop.
#4 Install a 3/8" x 3/8" x 48" braided flex with the 1/2" MIP
x 3/8" compression ell at the dishwasher.
#5 Install the drain hose supplied with your dishwasher at the bottom of the dishwasher.
#6 Install a 6' pigtail power cord to the power box under your dishwasher.
#7 Feed the drain line, power cord and water supply through the hole in the back of the cabinet at the bottom. As you push the dishwasher back into the enclosure, you will need to feed the 3 lines into the cabinet under the sink.
#8 Attach the water line to the open connection on the double stop.
#9 The drain line will attach to your garbage disposal.(If you have one) Be sure to knock the small piece of plastic out of the drain connection, and retrieve it out of the disposal, before connecting the dishwasher drain line.
#11 Raise the middle of the drain line as high as possible under the cabinet under the sink, preferably attach it to a screw to the bottom of the counter top. This will keep the dishwasher from drawing a back siphonage and getting a bad odor.
#12 Plug in the dishwasher. Assuming you have electrical under your sink. Otherwise an electrical outlet may need to be installed.
#13 Balance the dishwasher using the front legs. After you adjust the depth of the dishwasher, and the level. Use the 2 mounting screws included with the dishwasher to fasten the 2 clips above the door to the bottom of the counter top.
#14 Remove the installation manual and styrofoam from the tray, and turn the dishwasher on. Inspect for leaks as you run a cycle.
#15 Attach the bottom kick panels

You are done.

If you have any questions, please let me know.