How Do You Drain and Flush a Tank Properly?
When we speak of water heater draining, what we are really talking about is attempting to flush the tank of the sediment lying on the bottom of your tank and scale accumulations throughout. Draining the tank may be accomplished fairly easily utilizing the factory installed drain valve. However, most standard drain valves can run slowly or even become plugged with sediment if they have not been routinely used. At best the water will usually take about 20 to 30 minutes to drain, at worst it may not come out at all! For quicker draining and proper cleaning, we always utilize a full port drain valve for our service as shown:
Simply draining the tank through the standard drain valve will generally have very little effect on flushing the sediment out of your tank for several main reasons: 1) the bottom of the tank is actually about an inch lower than the drain port, 2) the orifice in the drain valve is very small and does not provide a clear pathway out, 3) the sediment is a settled mire which must be busted up and agitated to allow it to flow out of the tank, and 4) the accumulated sediment generally contains relatively large pieces that sit below the tank port and are too large and heavy to simply flow out without coercion. For these reasons there is very little chance of properly flushing a tank simply through draining.
Three common types of water heater drain valves installed as standard equipment on most hot water tanks. The round poly drain valve to the left, the plastic drain valve in the centre and the brass drain valve at the right.
The drain valve on the left only has a 1/4" hole to allow water and sediment to pass through. However, the housing does allow for an almost 1/2" straight flow through if the forward valve is carefully removed. The valve in the centre has just under a 3/8" hole for drainage, while the brass valve on the right has about a 5/16" port. They all require the water and sediment to make sharp turns and do not provide a straight through pathway when left fully assembled.
To facilitate proper flushing of your tank, the best way is to remove the standard drain and install a full-port drain valve. However, as the sediment sits mired below the drain port, it must also be disturbed and agitated. Our service accomplishes this by spraying water along the bottom and inside walls of your water heater allowing the sediment and loosened scale to exit through a full port drain valve, cleaning out the nasty accumulations that are hiding within your tank. This is what must be done to fully flush the tank and is what we do as part of our preventive maintenance service to keep your tank sound and running efficiently for significantly longer than the average water heater life span.
Full port drain valve shown. This has nearly a 3/4" opening which is 3.5 times the surface area of the largest port of the assembled valves as shown above and 2.2 times the fully open port of the disassembled round poly valve above. Pictured here is the style we use to properly flush the sediment from your water heater.