Rusty Tap Water: How to Flush Your Hot Water Tank

Rusty tap water coming from your water heater is a sign that your mains pressure storage tank could be corroding on the inside, resulting in rusty tap water supply. This could also indicate it’s a good time to get a new water heater, due to the chance that your tank may start to leak or bust if it is older than 8 years. If you wish to try and get a little more life out of your hot water system then you can give our solution a go. In this guide we will take you through some basic steps for draining & flushing your mains pressure water hot water system. If your not a handy person then we do recommend calling us to help with this type of water heater maintenance.

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NOTE: This process involves disconnecting pipe work and flushing the storage tank out to remove sludge and rust from the bottom of the tank.

Step 1 – Turn Off The Energy Source

Rusty Tap Water - Turn Off Power Supply

 

For an electric hot water system, you need to turn off the circuit breaker or a labelled control switch located at the main home power board. You should see the circuit breaker or switch as being clearly marked as Hot Water or maybe HWS  and with a clear indication of ‘on’ and ‘off’ direction. If you can’t find the circuit breaker or switch, you can contact us for guidance.

 

Rusty Tap Water - Turn Off Gas Supply

 

 

For gas hot water heaters there will be a control valve on the gas pipe line at the bottom of the storage tank generally close to the cold water supply pipe. If you are not sure on which valve to safely turn off then you can contact us for guidance. Solar hot water heaters are more complex and require expert handling, we advise you employ our technicians to carry out onsite inspection.

 

 

Step 2 – Turn Off The Water Supply

Rusty Tap Water - Turn Off Water Supply

 

 

 

 

 

 

To do this, first turn off the water supply inlet control valve which is usually located at the bottom of the water heater.This can be turned off by twisting or turning the valve in a clockwise direction.

Step 3 – Depressurise The Tank

The easiest method would be to simply turn on a hot tap nearby to let pressure out (remember to turn back off before disconnecting pipe work). Alternatively, at the water heater there is a temperature pressure relief valve with a lever that can also be eased open by the lever to give the same result.

Rusty Tap Water - Depressurise the Tank

Step 4 –  Attach A Drain Hose

Using suitable tools like a shifting spanner & multi-grips, disconnect the cold water supply pipe located at the bottom of the tank. Attach a drain hose to the bottom of the tank at the cold water inlet where it is coolest and make sure your hose is long enough to reach a drain or some other suitable place to deposit the drained water. NOTE: do not run the end of drain hose on to concrete path or drive way as the water from the tank may stain with rusty sludge when the tank is almost empty. The other don’t: it is not advisable to drain hot water onto your grass because the hot water left in the tank can burn the grass leaving a dead patch.

One additional recommendation is to turn the gas or power supply off 24 hrs before you attempt this process so the water in the tank has cooled down or the hot water stored has been emptied and replaced with cold water. SAFETY is very important and if you are not sure or confident in this process then call us for a service to carry out this maintenance.

Rusty Tap Water - Attach a Drain Hose

Step 5 – Disconnect Hot Outlet Pipe

The hot outlet pipe is located in most cases at the top of the tank. Again using suitable tools disconnect the hot water outlet pipe and the water from the tank will now begin to naturally flow through the drain hose to the drain.

Rusty Tap Water - Disconnect Hot Outlet Pipe

 

 

 

 

Step 6 – Flushing The Tank Out

The hot outlet on the tank is the best way to now back flush and run cold water from your garden hose back through storage tank. You can try just inserting the end of the hose into the tank fitting and holding this into position, or alternatively if you are confident to use a small piece of copper pipe with a compression fitting and nylon olive attached to your garden hose with hose clamp. This now can be mechanically fitted and tightened to allow full mains pressure to enter the tank through the hot water outlet fitting. Run the clean water through the hot water outlet of tank to back flush until the rusty water stops coming from the tank through the bottom drain hose.

Rusty Tap Water - Flushing the System

 

 

 

 

 

 

Step 7 – Reconnecting Hot Water System

Remove flushing and draining hose from the hot water cylinder. Connect the cold water inlet & hot water outlet pipes back up to the storage tank. Turn back on the mains water supply and open a hot tap inside the home to allow the air to bleed out. Once the water flow from the hot tap has pressure and flows correctly, turn off the hot tap and check the hot water cylinder for any leaks on the pipe connections. You can now turn back on energy supply. The hot water supply in your home may have some slight discolouration due to the flushing, but will become clear in a reasonable amount of time.

If you still experience dirty or rusty tap water after a couple of weeks then call us to evaluate your system and see if a replacement water heater is required.