Best process for flushing potable water tank

[hobo]

When we took delivery of our trailer in May, it had just been de-winterized that morning.  The water tank had a fair amount of volume in it so Hunter suggested that we leave the fresh water tank drain valve open while driving to David Crockett State Park to empty it.

 

We did close the drain valve under the street side bed when we got to our campsite per his instructions.  Since that time we have only used city water hookups for our water but the water tank still indicates it's about half full.

 

The trailer has been sitting at our house for a little while now (very hot outside) so I want to flush this tank thoroughly and want to know the best method.

 

Do I simply open the drain valve and let it empty and then refill with fresh water and empty again?  If so how many times do I do this?

 

Or, do I drain, refill and then open the drain valve and turn on the spigots till empty.

 

Experienced opinions greatly appreciated.

 

Thanks, HOBO

[Overland]

Here's my procedure -

Empty water tank.  Open drain valve, both faucets, Truma drain, and turn on pump.  Raise trailer nose and tilt trailer toward curb side.  Allow to drain until empty, then turn off pump and faucets and close Truma drain and drain valve.  Lower trailer nose to back level and tilt trailer slightly to street side.

Mix ½ cup of bleach into 5 gallons of water.  Set pump valves and pump all five gallons into tank.

Reset pump valves to normal operation.  Begin to fill the remainder of the fresh tank from the city water connection.  While tank is filling, turn on pump, and run each faucet, both hot and cold, until you smell chlorine and all the air is out of the system.  Allow tank to fill until water flows from the overflow by the door.

Let sit for 24 hours.

Turn on pump and run both faucets until all water is transferred to grey tank.  Refill fresh tank .

Let sit for 48 hours.

Empty grey tank.  Refill fresh tank and repeat step 5.  Empty grey tank again.