Water Heaters & Galvanic Isolators

[Joe Mullee]

I am replacing the water heater in my H34. Part of the literature is about galvanic isolators and whether or not one is needed. Is this the same as a zinc that I already have attached to the propeller shaft?

Thanks.

 

[sailingdog]

No. A galvanic isolator is a piece of equipment that is in-line with your shorepower connection and prevents low-voltage galvanic generated current from crossing from your boat or shore toe the other. This can help reduce problems with current induced electrolysis of the underwater metal parts of your boat. Read more about them HERE and HERE.

I am replacing the water heater in my H34. Part of the literature is about galvanic isolators and whether or not one is needed. Is this the same as a zinc that I already have attached to the propeller shaft?

Thanks.

 

[Don S/V ILLusion]

In addition to what SD mentioned, any boat which is frequently connected to shore power should have a galvanic isolator or preferably an isolation transformer although the latter can be more expensive. I think the literature to which you refer relates more to the shore power connection than simply having an elec water heater.

 

[Skip L]

The galvanic isolater is a device that goes between the water heater and the piping to prevent the carbon steel of the tank reacting with the copper pipe used to plumb most systems. these are used on most house installations.

 

[Steve Dion]

This problem is NOT isolated to boats and really has nothing to do with electricity from the boat.

"If you recall from high school chemistry, two dissimilar (different) metals, when placed in an acidic solution, will create a battery. And one metal will usually erode away as the chemical reaction progresses. The other metal may have a buildup of new material, which may be a chemical combination of the eroded metal and the acid. Since virtually all domestic water is slightly acidic or slightly basic, this electro-galvanic action can occur in any metal plumbing system.

When copper and steel pipes are connected together directly, the "battery" has a path for electrical current to flow. (This current is tiny, and the voltage is not a safety hazard.)

If the current cannot flow, because there is no electrical connection (interrupted by the plastic insulators) then the "battery" never discharges. In theory there will always be a small voltage between the different metals. The metals do not erode.

This electro-galvanic action is called electrolysis and in time it will eat pin holes in copper pipe. Dielectric Unions are insurance and well worth the money. If you had leaks at the threads did you tape them with Teflon Tape before installing?"

My father was a plumber and he never installed a water heater without a dielectric coupling. He did replace a lot of copper becase the previous installer did not install one.

 

[Steve Dion]

This issue about electro-galvanic action should not be a problem if you are joining the metal from the water heater to a plastic plumbing supply (which I must assume your vessel still has).

 

[sailingdog]

I've never heard the plumbing part called a galvanic isolator. I've heard of dielectric unions, and used them, but don't really see a need for them on a boat, where the plumbing is generally plastic hose. While, I've seen copper pipe used on a boat, it isn't very common or very smart to do so.

 

[Bill Roosa]

We are talking apples and onanges

A galvanic isolator (more properly called a dielectric union) is a plumbing part that "electrically disconnects" the water heater from the metal plumbing supplying the faucets.
A galvanic isolator is an electrical device that goes into the ground circuit of the boat AC circuits and protects the boat from corrosion.

The manual is using the wrong term. You do not need a dielectric union if your plumbing is plastic. You should think about installing a galvanic isolator to protect your boat though. You don't need a galvanic isolator to get the water heater working however.