By Bob Eustace
Without doubt, the US-made Suburban hot water system is the most popular brand for use in motorhomes in Australia. We are onto number three in our motorhome and have had zero trouble over the years. We have, however, religiously replaced the sacrificial anode at least once each year.
The anode is there to protect the innards of the hot water service. It does this by ‘sacrificing’ itself – sort of like the chrome-plating process but in reverse. Many domestic hot water systems use exactly the same method. Truma, Atwood and Dometic use stainless steel tanks and therefore do not need an anode.
All Suburban models do, yet they remain very popular. In our view, this is possibly because of fast heating and quiet operation.
The photo at the top of the page (above right) shows an anode after six months’ use in SA, as compared with a brand new one. Areas with highly mineralised water definitely wear out anodes more quickly.
A new unit is not expensive, and costs around $28.
If you are on a tight budget and have a plumber mate, just ask him for all his old domestic anodes. These are very long and usually wear away on the far end only, so they can be cut down to suit your Suburban.
The anode is always located at the bottom front of the unit. You do need an oddly sized socket or spanner, 1 1/16in AF or 27mm. It can be awkward using a spanner, so beg, borrow
or steal a socket if you can. An Eclipse works well and costs about $8.70.
Before starting, make sure that the hot water is cool enough not to scald you and then turn off the 12V pump.
Disconnect the town water if you have it hooked up. Depressurise the system by turning a hot water tap on and letting it run until it stops.
Unless you want to be covered in the white gunk that lives in the tank, further depressurise the tank by pulling up the relief valve until water stops gushing out. The thinkers among us will now be wondering why this happens, as all the pressure goes when you turn on a tap. Not so – many installations have a one-way valve (a check valve) to stop reverse flow.
After completely removing the anode, close your hot water tap and turn the pump on. Water should gush out of the anode hole, bringing with it heaps of revolting, jelly-like gunk. This cures you for life from using hot water to cook with or making a cuppa. You can, if you wish, squirt a hose in the hole just to be sure. A friend gave us a dandy gadget he bought in the USA.
It was a piece of 1/4in copper pipe soldered onto a brass hose fitting. It worked OK, but really was overkill.
As soon as the water runs clear, turn off the pump and screw in the new anode. Many anodes come with Teflon sealing tape already on the thread. If it is damaged, missing or looks iffy, put on a new bit. You can buy it at any plumbing supply shop. Watch out though, as there are two types: water or gas.
Turn on the pump and partially turn on one hot water tap. Now the water will flow very slowly, if at all. Don’t panic, because this is normal. All that is happening is the hot water tank is filling up. When the pump stops as you turn off the tap, you will need to bleed all the air from the tank: lift up the handle on the valve (usually in the top left) and wait until water flows continuously.
This gets rid of any air right at the top of the tank. In most installations this flows into the hot water system as very few have an overflow pipe connected.
Clean up your mess and the job is finished. This is an ideal project for those new to DIY and it shouldn’t take more than 30 minutes.
To avoid nasty smells developing in your water system, under no circumstances use an anode made for marine use. We always buy ours from RV dealers as they usually don’t sell marine ones, so there is no chance of a mix up. If you buy a used RV and have a disgusting smell in your water, this could be the reason. The best idea could be to replace the anode before messing around with water purifying tablets, bleach and so on.