Hot Water System Anode

Another small maintenance job that fits well within the capabilities of the most basic of handymen/ladies. This job is another that will save you considerable cost both in outsourcing the maintenance, and in rectifying the damage that will result is avoiding it altogether

Many vans today have a HWS (Hot Water Systems) and of the 3 more common ones we’re only interested in the most common of the 3 types, the gas/elec storage HWS. The other two HWS’s are the instant gas and the stainless steel storage unit.

The most common gas/elec storage type HWS have whats called a sacrificial anode, which is a serviceable maintenance item that you should make yourself familiar with and not overlook. The average household storage HWS also has a anode which can be replaced and extend the service life of the tank for many years. The anode is a replaceable rod that helps to prevent the corrosive elements contained within water from attacking the steel storage tank and destroying the HWS from the inside out.

Water contains corrosive electrolytes and minerals which attack metals and cause what we know as rust. The steel in the tank is a less active metal and the anode is a rod of highly active Magnesium. The corrosive elements will attack and corrode the anode before the less active steel tank. So long as you have a anode, your HWS tank will serve you for many many years.

The rate or speed of corrosion of the anode will depend on your location and the quality of the water. For us we would average around 12 months from an anode, although this is extremely variable and we still check our anode every 3 or 4 months.

A caravan storage HWS replacement anode is worth around $25 and will be found in every single caravan retail accessory store.

Checking and/or replacing the anode is very easy, requiring a single tool, and will save you thousands of dollars replacing a corroded and failed hot water system.

Now for the warnings, safety and important stuff. There’s nothing complex here, mostly common sense. Its a very safe and simple job so long as some equally simple oh&s precautions are followed.

Always carry a new replacement anode with you. There’s not a lot of point checking the condition of the anode if there isn’t a replacement one on hand.

Being a storage HWS the contents of the tank will be very very hot, much hotter than the water from a hot water tap which is cooler due to a requirement to run the water through a tempering valve. In changing the anode you are dealing with the tanks water, and not the tempered tap water so ensure the HWS tank water has cooled sufficiently to undertake the work safely. HWS storage tank water is required by Aust plumbing codes to maintain a water temp over 60deg, typically 65deg to limit growth of Legionella bacteria. Hot water at 66deg will cause a major burn within two seconds exposure. An inline tempering valve is installed to all storage HWS to reduced hot water temps to a safer 50deg where a 5min exposure is required to cause a significant burn

The best advice is do the anode maintenance when the hot water has been turned off for some time, after the HWS gas and 240v has been turn off the and then a hot tap has been opened long enough until the water temp has dropped sufficiently to enable a safe water temp environment to remove the anode.

The single most important safety point is to de-pressurise your vans water system, I cant stress this enough. The plumbing system is a charged system and potentially pressurised upto 500kPa. The hot water system holds a lot of pressure and removing the anode in this condition will almost certainly result in property damage or injury. Under tank operating pressure the anode will fire out of the water tank like a weapon of mass destruction. Ive done it, and was very lucky to be have able to father more children.

De-pressurising the plumbing system is as easy and simple as opening both a cold and hot tap. Before you start the process though disconnect the van from mains pressure water connection, double check the 12v water pump is turned off and turn off both the gas and 240v to the unit.

Cracking the taps to release system pressure is a great opportunity to feel the temperature of the hot water to ensure its at a safe temperature to remove the anode. You should already be de-pressurising your plumbing system when your van is in storage anyway, if not then you will be now.

The vans plumbing system has a series on non-return valves which are designed to stop back flow and as a byproduct these valves will maintain plumbing system and HWS pressure even with the van is disconnected from the mains water and with the 12v pump turned off. Opening both a hot and cold tap will relieve that pressure.

The anode is located in the water storage tank, and opening the outside HWS cover it will be identifiable (in the case of Suburban) by the large 1 1/16 nut. Check either the manual or Google if you cant readily locate your anode. Its can be little tricky to get to so you’ll need either one of the special expensive accessory tools … or just the 1 1/16 socket from your tool box.

The anode is a standard thread (clockwise on, anti off). If it hasn’t been checked or changed in a while it may be stiff and need a little bit of persuasion. Theres no torque setting required when replacing the anode, with some plumbing tape around the thread just enough tension so it doesn’t leak.

When you removed the anode the first thing to expect is the contents of up to 25 litres of water will start glugging out by gravity, so ensure your in a place where 26litres of water pouring out wont cause an issue. The water will likely contain a white chalky granular substance which is the remnants of the corroded anode. This stuff is harmless and an indication that your anode is effectively doing it’s job.

You’ll know what a new anode looks like by comparison (because you’ll have one nearby, in case it’s needed) and the you’ll note that the anode removed from the HWS looks very different from the new one…. its will look like its been corroded away and that’s no coincidence, because it’s exactly what you’d be hoping to see. With the anode removed and the tank now empty of water, its a good idea to flush as much as possible of the chalky granular remnants of the anode from the bottom of the tank.

A garden hose is generally too large to flush the tanks because it almost fills the anode hole. We have a small thin length of small clear hose jammed onto the a hose connector which does the job for us.

Its at this point with the old anode in your hand you’ll need to decide if the anode needs replacing, or has enough ‘meat’ for a few more months. Check the lengths of the old and the new just to be sure (longer anodes can simply be cut to fit)

In our experience anodes generally last us around 12 months so that’s around $2.00 per month in anode protection. A HWS unit replacement including installation is worth well over $1000. A HWS cared for with the most basic handyman skills, using very simple and straight forward preventative maintenance is free and a maintained HWS will last many many years.

75% percent maximum anode consumption is both the common sense and the recommended replacement time anyway. If my anode is more than 50% consumed it gets replaced regardless. Putting it back into the HWS is risking my HWS for the grand total saving of $2 per month and my best guess how much longer it ‘might’ last. Im not convinced that’s a good economic gamble, or worth the risk.

• 

When replacing or reinserting the anode just bear in mind, particularly with the new anode, its quiet long and heavy and your only holding it by the extreme end with only 2 fingers in a cramp position. Make the conscious effort to keep the anode as parallel as possible when threading it to avoid cross threading.