Zinc anode install

[RecurveArcher]

I've read various thoughts on the effectiveness of sacrificial zinc anode's, and whether or not they're necessary; thinking of installing one because I figure it couldn't hurt. I've seen the recommendations for the $17 '6 lb Crab/Lobster Pot Zinc Anodes' on Amazon and the numerous posts saying to connect it tot he bonding system and bury it in damp soil, but nothing that shows pictures or really gives any details on exactly how to do that.

Our equipment room has a square cut out of the floor where the PVC lines come in; in there is also where all the grounding wires connect:

Is it really just as simple as burying the anode, connecting it to that ground stake with the rest of the grounding wires, and then keeping the ground damp where it's buried? Or is there something else to it?

What's the best way to attach it? Copper wire either clamped and screwed onto the anode or wrapped around it?

 

[JoyfulNoise]

No it's not that simple

Sac anodes must be bagged in a cotton anode bag and back filled with a mixture of gypsum, bentonite clay and sodium sulfate. Just sticking a zinc bar in the ground will not work as the anode surface will deeply polarize and build up a non-conductive oxide scale that will render the anode useless.

You also need to size the anode for the area that it's protecting. If your anode is undersized relative to the area it is protecting it will receive excessive current and also suffer depolarization effects that will damage the anode.

What is it you are actually trying to protect?

 

[RecurveArcher]

Theoretically anything that it can protect (equipment, auto-cover rails, plaster, etc.) but one of the big items would be the pool walls, which are a painted-over stainless steel that are (contrary to the name) very stained. Lots of rust showing through, some even bubbling up. The pool was renovated about 20 years ago and I don't think properly maintained. It needs to be drained, rust scraped and patched, acid washed, re-painted, etc., but the contractor said the rust would likely keep coming through and said we'd probably need to do touch-up paint every year to keep any new rust spots covered as much as possible. I thought maybe an anode would help to slow down any deterioration of the walls, both until we get it fixed and afterwards.

Basically, I figured it would be a relatively low cost addition, so if it does any good, probably worth it.

Here's a picture of the walls with rust coming through; the light housings and skimmers are all pretty rusted as well:

 

[JoyfulNoise]

Yeah, that's some pretty extensive/bad corrosion. I hate to say it, but a 6-lb anode attached to a bonding wire is literally doing nothing to protect the pool walls. Anodes must be match in area to cathodes (aka, your pool walls) or else the anode will be overwhelmed with current from the larger surface area. The weight of the anode will theoretically only tell you how long it will last, not if it will be effective. The proper way to cathodically protect a large structure like that is not to use sacrificial anodes but to install an ICCP (Impressed cathodic current protection) system. It's an electronic device that supplies current to the metal object to protect it. Because the steel pool walls are a huge, buried surface area, it's impractical to use sacrificial anodes. A cheap sacrificial anode method would be to do like they do on the hulls of ships and physically weld magnesium (or zinc) anodes to the hull surface at periodic increments. That then causes the anode to slowly dissolve over time as opposed to the ship hull. But that only works because anodes can be visually inspected and replaced as-needed. In a buried tank scenario like yours, you could only do that once and then never again unless you dig up the pool.

Sorry, but you definitely have a big remediation job on your hands there in the future no matter how many anodes you buy....

 

[gwegan]

Just to pile on a bond wire attached to a ground rod in your equipment room does nothing to actually bond the pool. Ground rods generally add nothing to a pool or to bonding. For your pump, heater and SWG bonding to be effective they need to be connected to the bonding system at the pool.

 

[jmu7b6]

Have you found out a solution yet for your pool walls? I have essentially the same pool and I'm starting to have rust spots as well, not as bad as your photo but I'm trying to prevent that from happening.

 

[gwegan]

Rust problems with pool walls are generally caused by normal oxidation action. Galvanic corrosion usually has little to do with rust on pool walls, The best way to solve problems with metal pool walls is proper coating when installed and keeping the pool area free of water. After installation solutions are to drain and replace with properly coated walls and again keeping the pool area free of groundwater.

 

[ps0303]

In my opinion, sacrificial zinc anode's for pools is a waste of money. Now if you're putting them on your boat because you use the boat in the ocean, then they are worth it.

Just my opinion.