Sacrificial Anode

[Grumpy John]

I was wondering if double filtering the water before the hot water tank helps improve the life of the sacrificial anode. I know they aren't expensive when compared to the cost of replacing a hot water system, but the last anode I fitted only lasted for a 5 week trip to the Birdsville Races. I know the water in outback Queensland is pretty harsh, but I didn't expect the anode wear this quickly. Funny how most of the wear is at the threaded end, is this normal?

374336

[cava]

If the threaded end is where the hottest water is (ie at the top of the tank), then yes.

[Grumpy John]

Forgot to say that this is a caravan (http://caravansplus.com.au/catalog/product_info.php?products_id=8521) HWS.
The anode is sitting horizontal at the bottom of the tank.

[malb]

The threaded end is generally the closest to a different metal (tank), and hence most likely to erode. Depending on tank materials and structure, there could be quite a few metals involved at that point, anode cap (brass), tank wall (MS or copper), tank bush for anode (MS, copper or brass) and the brazing/welding alloy (possibly 5-8 metal elements).

The original glass lined MS tank in our former home had a vertical anode about 1m long, it always ate out from the cap down. It was replaced with a SS tanked unit without an anode that was still going well after 21 years when we sold last year. Seems that they picked a SS grade that was extremely inert and the anode would have introduced additional metals and degraded the overall lifespan rather than enhance it. An identical unit installed at my uncles place 26 years ago has been totally fault free except for a burnt out thermocouple in the pilot system.

[Grumpy John]

Thanks for that detailed explanation Mal. So apart from nicer tasting water and reduced calcium buildup in the shower head the filters will have little, or no effect on the wear rate of the anode?

[Yanis]

... the filters will have little, or no effect on the wear rate of the anode?

Correct. The anode is there to cater for the dissolved minerals. Suspended particulate is all that filters per se will eliminate. You need a "water softener" or a reverse osmosis system to eliminate (or convert) dissolved salts which is what causes your corrosion.

John

[Grumpy John]

One thing I've learnt from this is that you don't use the hot water for cooking or making a cuppa unless you have a filter fitted AFTER the HWS.

[dai sensei]

What sort of hot water service is it John?

[Grumpy John]

What sort of hot water service is it John?
A Suburban, check out the link in post 3.