Need portable DW but have low hot water pressure in apartment

pressure on what? your blood circulation? tire in your truck? bicycle?

you need to provide more detail, telepathy do not work and we are not living with you...

Pressure inside tank builds up?
Follow same steps used for low pressure on following link
http://waterheatertimer.org/Low-hot-water-pressure.html

Pressure below 80 psi is fine
Gene

Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) If possible, it is Best to solve pressure problem before installing new shower.
http://waterheatertimer.org/Low-hot-water-pressure.html

2) If the cold water has good pressure, then Electric shower could fix problem ... but shower would have to be connected to the cold water line and not the hot.

3) Seems the expense of adding a electric shower would be greater than having plumber fix low hot water pressure.
Assuming you have access to plumbing pipes, and this is not apartment building.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Question is not clear.
Are you trying to clean out water heater, or clean out clog in pipes? Or some other problem?

Open following links to help identify problem, and then add a comment.
http://waterheatertimer.org/How-to-clean-sediment-out-of-water-heater.html
http://waterheatertimer.org/Low-hot-water-pressure.html

Setting yourdishwasher temperature is done by your hot water heater. If you need to lower the temp, turn down thehot water heater. If you need to raisethe temp, turn the hot water heater up.

For your answer on where to purchase a Carocelle Brand dishwasher, Here it is. You might only find these in certain "junk shops" like a Saver's or Goodwill. You might find one on the Craigslist site. You will not be able to find any more new ones, since Carocelle Industries folded. MAYBE, and a big maybe ebay. Note before you buy... If you have a "water saver" faucet, this item won't perform well. Same goes for low water pressure... including low pressure on a top floor of an apartment building.

You have clog in the water line.
Since all hot water pipes are involved, clog is probably near water heater.

Buy pressure gauge at hardware store that threads onto hose connection.
Brady BTG 100 at Amazon
Picture of gauge

Check outdoor pressure for baseline pressure in your home.
Turn off electricity to hot water heater for an hour or two so there is not scalding water.
Open drain valve on water heater to see if water heater is clogged with sediment.
http://waterheatertimer.org/Water-heater-will-not-drain.html

Put pressure gauge on drain valve and compare with outside pressure.
Open hot water spigot on bathtub and see if tank pressure drops ... if tank pressure drops significantly with bathtub spigot on, then clog is on incoming cold water before tank, and could be on outgoing hot water pipes too.
If tank pressure stays about the same, then clog is on outgoing hot water pipes.

Clog can be sediment caught in cold water shut off valve located above tank. Open and close valve and test pressure again. Take apart incoming cold water pipes above tank and check for sediment. Replace valve. Look at condition of cold water nipple on top of tank.

Sediment caught at hot water elbow near tank.
Sediment can fill up old pipes. Take apart hot water pipes above water heater and see condition.
Look at condition of hot water nipple on top of tank.
You may have to take apart pipes up to first or second elbow.

Pipes can decay at joint where copper pipe connects to galvanized pipe. Check for copper to galvanized connections on cold or hot pipes and replace section of galvanized pipe. Copper pipe will probably be good, the galvanized pipe will deteriorate. Replace copper-to-galvanized joint with 3/4" non-conducting union from hardware store

there is calcium in water and it builds up around the pump and the flow you typically have to take it all apart to clean it or there is crud in your drain inside the dishwasher, basically you are swishing around the dirty old water and food particles, Ralph this is from not rinsing dishes first and using special dishwasher soaps to prevent the build up thus clogging pump and exit lines. pull the pump apart if you dont find clogged filters.

Shut off the water supply and open your faucets, and apply air pressure (min. 30psi) to dislodge any blockage in the pipes.

If the build up is really bad you will have to take the whole unit apart. Remove all the elements and break up what you can with a wire coat hanger or something similar. Use a product like Lime Away. Check the elements carefully as they can be damaged by build up. You probably have one or more burned out from this. Check continuity and replace if needed. Make sure the wattage is the same as the old one. If it is a different shape make sure no element touches another. This should solve your problem