I'm trying to install a new dishwasher but the pipe fitting used to feed hot water to the new machine is a 1/2-in while my old one used a 3/8-in pipe. Home depot said there was No adapter and my only choice was to spend 80 bucks on new copper tubing but I want a second opinion.
You do not indicate the sizes of the piping in question, nor what the rating was for the PVC pipe initially installed. This may have some bearing on the method of repair because copper is now very expensive and SCH 40 copper pipe would be both difficult to find and exceptionally expensive if you did. Also, copper is already an extravagant material to use on chilled water piping (not small tubing) when flanged and welded Sch 40 carbon steel is the most commonly used material in larger sizes and screwed galvanized pipe is used for most 2 1/2 and smaller. PCV pipe needs to be supported more frequently than steel pipe and will have a much lower service pressure rating. However, your operating pressure may still be within the allowable range. At these service temperatures, thermal expansion is not going to be a problem regardless of what materials are used. If your ONLY problem is that some joints leak, it is probably because the surfaces were not proplerly prepared and/or the cement was not allowed adequate time to set before the piping was moved around. I would recommend that in this case you forget the copper ( forever) and investigate the cutting-out and proper replacement of the several deffective fittings with CPVC Sch 40, piping and equivalent solvent joint fittings.
dishwashers have a 3/8 female iron pipe thread (fip) you can use a 3/8 fipX 3/8 compression adapter or a 3/8 fip X 1/2 compression adapter. Any plumbing supply house will have these. If you need to change sizes, you can get a 1/2 conp. X 3/8 conp adapter. What you want to ask for is a dishwasher ell if it has a 90 degree bend.NOTE; all dishwashers have 3/8 fip coming out of solenoid
There are a couple of issues you will need to deal with. First is that the solenoid that allows water into the dishwasher almost always has a female threaded opening at the bottom. This requires an elbow with male to male threads. It is never supplied with a new dishwasher so you'll need to purchase one. Secondly, depending on the distance from the hot water shutoff to the elbow at the front of the dishwasher you probably can buy a braided steel water supply line for about $20. You'll need to know the length as well as get the right sizes of compression nuts that they come with. Typically you'll need 3/8 or 1/2 compression for the end attached to the shutoff and 3/8 compression for the elbow you need to buy. If you can't tell the size on the shutoff end, remove the pipe and take it with you. Don't forget Teflon tape as well.
