PLUMBERS - CPVC as dielectric coupling?

It has been recommended to me that I use dielectric couplings on my water heaters to reduce corrosion. I suppose it is just a matter of price, but will a CPVC coupling do as a dielectric coupling? Don't expect to be sweating any joints near them.

Its not going to do anything to stop iron from rusting.

Is your house plumbed in copper or plastic?

The dielectric fittings are there to prevent galvanic corrosion between dissimilar metals. If your house is plumbed in copper pipe you don't want it in direct contact with the steel of the hot water heater. So the fitting electrically insulates the copper from the steel.

If your house is plumbed in plastic then dielectric fittings won't make any difference either way.

Without knowing the answers to the questions that have been raised, all I can say is that if you are contemplating using female NPT PVC fittings, they are a leak waiting to happen.

The plumbing is all copper, but the nipples on the water heaters are steel. I seem to be getting a lot of corrosion (green copper) near the water heaters. I thought to just put a CPVC female/male coupling between the nipples and the copper. Could the green just be an excess of flux?

I don’t like copper directly fitted to steel. I use flexible stainless steel hoses. I don’t like the ones that are braided. They can have a reaction to the liner and put off black residue in your water. They are lots easier to change if you see a small leak. I would never use pvc or cpvc anymore. It’s probably against code in most places.

I've never known a plumber to clean a joint after soldering so the "green" could very well be from the solder. You can clean that off easily with a mild acid solution. The most effective is muriatic acid which will leave the copper as clean and shiny as the day it was made BUT be cautious with muriatic - the fumes are bad and it will burn skin. Dilute it and wear rubber gloves. Dip a rag in it and wipe the corroded area. Rinse with another rag soaked in clean water. The results are instant - no soaking and waiting required.

The green is either flux or a corrosion from a small leak. Just use teflon paste or tape and torque new copper threaded fittings onto the steel threaded fittings coming out of the water heater. The more fittings and different types of materials you use, the more opportunity there is for problems down the road. Never had an issue in four decades doing as described.

How many foot/pounds are you recommending ??

I use clear ammonia to clean solder joints after soldering to remove and neutralize any flux.

crank it up 'till it strips or breaks, then back it off 1/2 a turn........................ [i couldn't help myself...... ]

I have been a plumber for 35 years, and yes I wipe every solder joint. We have never met but now you know att least one plumber who takes pride in his work.
To answer the OP"s question, brass is a neutral metal which will not corrode when in contact with steel threads on a water heater.
I would not mix CPV with the copper as a dielectric union.
Ed

Funny you should mention this - I was think this when I read the original post - most "threaded" connectors that copper solders into are brass. Yes, you can get copper, but brass are more common.

Don't most new residential water heater installs opt for flex-hose lines anyway?
I just replaced an old water heater that had dielectric couplers on it and they were corroded solid anyway; just cut them off and sweated on normal fittings for the flex hose.

It depends on the the age of the heater. The new ones I see have a galvanized steel nipple with a plastic liner on the inside already installed. Flex connectors install directly to those with none of the problems you are having. Before that came along, a good plumber used a brass nipple straight out of the tank.