This was sent to me by a workmate, and apologies to any plumbers out there. Any more tips out there?


No I haven’t gone mad and started communing with the spirit world…A Sacrificial Anode is found in your hot water system. It’s there to corrode before your hot water tank does. If you have a hot water system with a storage tank (including gas and solar ones) it has a sacrificial anode in it.
“So what” I hear you cry! Well, the anode works by corroding before anything else does so it is a consumable item, and wears out. When it does, corrosion starts on the tank which eventually starts leaking, and then you need a new hot water cylinder! All because a $40-50 part wasn’t checked every 5 years or so.

Now you are asking, “Why is there no sticker on the cylinder saying to check the anode??” Well if I was in the business of selling hot water cylinders then why would I tell my customers how to make them last forever, when I could sell a new one every 10 years or so!


So what do you do about it…if your hot water cylinder is over 5 years old, you need to check it, or have it checked by a plumber.

Checking it yourself is not rocket science!

Tools needed:

A socket set with a 26mm and 27mm socket and maybe a piece of pipe to put over the socket handle to give you extra leverage.
A flat bladed screw driver
A roll of Teflon thread tape

First: Find your hot water cylinder

Second: Turn off the tap on the inlet (near the bottom) or turn off the mains tap

Third: Relieve the pressure in the cylinder by operating the relief valve near the top of the tank (incidentally you’ll see a notice next to it saying operate this lever every 6 months- it’s a good idea anyway, as if the valve starts leaking it can cost you a lot in lost hot water or a burst cylinder if it doesn’t operate)

Fourth: Prise the plastic cap off the middle of the top of the tank. Underneath you will see a plug, probably half covered in insulating foam. Clear this foam away so you can get the socket onto the plug.

Fifth: Release the relief valve again just in case, you shouldn’t hear any water flowing, then use the socket to unscrew the plug. It will take a lot of force, and unscrews normally (anticlockwise), make sure the socket is a tight fit on the plug and use the pipe for extra leverage if needed.

Sixth: Pull the plug upwards out of the cylinder, there should be a large metal rod attached to it. When it was new the rod would have been the same diameter as the plug and nearly extend to the bottom of the cylinder. Try and estimate how much metal is left vs how old it is, then you will know when you need to replace it. If it is more than 80% gone you may as well replace it. Plumbers have a talent for putting the tank where you struggle to get at the anode, you may only be able pull it some way out of the tank (they also have a vested interest in you replacing your hot water cylinder, they make much more money out of that!). It corrodes from the bottom up and top down so if the top seems pretty slim chances are the bottom is too, though it may be thicker in the middle.

Seventh: So you need a new one. Write down the make, model and size of the cylinder and go to your plumbing supply and get one, they cost anywhere from $30 upwards. If you need to drain the cylinder so you can tilt it to get the new anode in, good luck, you’ll need a garden hose and some fittings and some creativity. (Actually you can get bendy ones for this situation - Easty)

Eighth: The final step. Use the thread tape to seal the plug and screw the anode back in. There is a catch though. There needs to be metal to metal contact between the plug and the body of the cylinder, so don’t wrap the whole plug in tape, leave a gap so the two threads can contact.

(Solar Hot Water systems have the same thing, only everything is on its side, with the plug in the middle of one end of the tank and you will need to half drain it to check the anode)

Feel free to pass this on to anyone who doesn’t like wasting money

On the subject of anodes, guess which corrodes when you get lead (like a sinker) and aluminium (like a tinnie) touching, with an electrolyte (like seawater) between the two?

Just changed mine, piece of pie. Took 10 minutes. Bendy anode cost $95.00; plumber's quote to do it was $380. (dodgy chain mob). Only problem I had was the original anode wasn't of the bendy type, but had corroded sufficiently to be able to bend it as it came out. (only small gap between top of tank and floorboards). Now to fix the laundry door for double brownie points sunday

Easty "checking yourself is not rocket science" Just a word of caution from a corrosion engineer that runs an anode manufacturing plant but not for domestic hotwater service anodes. There is a little more to the correct procedure than described. There are actually three types of anodes produced for hot water service tank applications. Magnesium high potential or M1, Magnesium Standard Potential or M3 and Aluminium A6. The correct anode material choice is based on the Resistivity of the electrolyte (water). Most applications will be fine with either M1 or M3 anode material and you down in Tasmania with the nice pure (high resistivity) domestic water supply will have no problems. Some areas Adelaide and parts of WA where the water resistivity is low (tastes like crap too) the use of the incorrect anode can lead to hydrogen evolution and a build up of hydrogen gas in the tank. This has been known to go bang with disasterous consequences. Best to check with the hotwater tank manufacturer which anode is recommended in your area.

Hard water here also, there's a couple of plumbers in Mt gambier (SA), that make a living by booking in 'anode replacements' for hot water systems every 3 years, for a fee. They're fully booked, and have their appointments 'pre-booked' annually, (kinda like the firies with extinguishers every 6 months). Easy money, I say.

Good luck to them!!!