Dielectric water heater fittings

reading through old threads there are some here who don't think dielectric fittings work. My understanding is that they serve to seperate two dissimilar metals to prevent corrosion caused by a dielectric reaction. I found four types. The copper flex and large nut type seem to be truly dielectric. The two types of nipples seem to still contact the nut at the threads. Why then are they labeled as dielectric?









Same fitting dissassembled



Note where the brass insert goes into the steel nut, there is only about 1/16" air space although the nut should torque down straight so there is no contact unless you managed to put it on crooked or if the plastic insert was crushed

maybe should have this moved to water heater forum.


I learned over there that the BrassCraft Speedi Plumb® PLUS Engineered Polymer Braid Water Heater Connectors are fully dielectric.


Speedi Plumb® PLUS water heater connectors with Engineered Polymer Braid provide superior flexibility and corrosion protection. Speedi Plumb® PLUS connectors combine advanced corrosion technologies with state-of-the-art manufacturing to provide the most flexible, corrosion resistant water heater connector available on the market today.

Patented Flexibility
The Speedi Plumb® PLUS patented polymer braided jacket is specially engineered to be less abrasive and more flexible than stainless steel. The polymer fibers bend freely, without kinking or crimping, making installation easier, especially in cramped quarters.

Superior Corrosion Resistance
Our braided jacket is constructed of high temperature, polymer-coated fibers. These fibers are specially engineered to resist corrosion from 100+ household chemicals that can corrode and deteriorate stainless steel braiding.

No Dielectric Union Needed
The engineered polymer braid and EPDM rubber core are non-conductive materials. The absence of dissimilar metals within the waterway eliminates the potential for corrosion at the connector and the need for a dielectric union.

The Preferred Seal
The nitrile rubber washer used in the Speedi Plumb® PLUS connector requires less torque to seal and is more resilient than PEX to rough nipple surfaces. Longer connector nuts mean greater thread-to-thread engagement and a better seal to lined nipples.

A Perfect Fit to PEX
A specially engineered brass adaptor allows installers to connect directly to PEX pipe; available pre-torqued on a Speedi Plumb® PLUS connector or individually packaged. Speedi Plumb® PLUS connectors are also available for direct connections to iron and copper pipe.

Certified to ANSI/ASME A112.18.6

Made in the U.S.A.

The plastic lining does not allow the water to touch the metal therefore it is dry and no corrosion...

fittings

The air space is irrelevent, the plastic is separating the two metals, but since the electrolytic action occurs through the water, the do not perform any function, other than to "look pretty". The flexible supplies also have a plastic "isolation" so the two metals are not touching, and the nipples have a plastic liner which is supposed to isolate the metals from the water. As anyone who has been in the business for more than a couple of years knows, the water DOES attack the metal behind the plastic sleeves and since it is a fairly poor grade of metal, the nipple can FILL with corrosion and restrict the water flow, or generate a lot of "red" water at the hot water faucets.

Two opposing opinions from two experienced plumbers

seems practical about the nipples they still contact metal

but I'm not buying your religion against a true dielectric