Hi @ssk12 ,
Does the washer have both hot and cold water supplies attached to it.
If so when you shut off the main house tap, if you have a hot water storage tank in the ceiling or on the roof, did you remember to also shut off the main house hot water tap so that hot water is not going into the washer, due to a faulty hot water tap that the washer is connected to?
If it is not the hot water supply then if the washer is filling when the main house water tap is closed then maybe that tap is not closing properly and also the tap that the washer is connected to isn’t either.
Try fully closing the main house tap and opening any other tap such as the kitchen tap or bathroom tap and check if water continues to come out of them. Initially there will be a flow of water as the pipes drain so be prepared for this but this should eventually stop.
If water continues to come out even at a trickle then the main house tap isn’t closing properly.
If the water comes out fast all the time you’ve closed the wrong tap.
If the water does continue to trickle out when the main house tap is closed, remove the washer’s hose from the tap that it is connected to, and making sure that the tap is closed check if water is coming out of it.
Remember to close the main hot water tap as well when you are checking for leaking water, just so that you don’t get confused as to where the water may be coming from
You may have two problems so take it one at a time.
You may get a bit wet trying this ;-)
Turn off the tap that the washer's cold water inlet hose is connected to and remove the hose from the tap.
There will still be water in the hose so have a bucket handy.
Check if there is water coming from the tap. Ideally there should be none.
Next turn off the tap that the washer's hot water inlet hose is connected to and remove the hose from the tap. Check if there is water coming from the tap. Ideally there should be none.
If this is what occurs then the taps are OK. If not whichever one is still dripping water then that is one problem but it isn’t the cause of the tub filling when the machine is not in use.
If both taps seal off the water OK, (or even if one doesn’t) reconnect the washer's cold water hose to the cold water tap and turn on the tap.
Check if water flows into the tub. It shouldn't. Give it a bit of time to make sure that it doesn’t. If it does then there is a problem with the washer's cold water inlet solenoid.
If there is no water coming in then do the same with the hot water hose. reconnect it to the tap and turn on the tap and check if water flows into the tub. It also shouldn't. If it does then there is a problem with the hot water inlet solenoid.
If there is a problem with a solenoid turn off the appropriate tap that supplies the “faulty”solenoid and then disconnect the hose from the washing machine. Check the filter in the end of the hose fitting that connects to the washing machine end (or the machine’s water inlet connection, it varies with makes where it is located) to make sure that it is not damaged etc. This filter is there to prevent grit etc entering the machine where it might cause the solenoid not to close properly.
Unfortunately faulty solenoids cannot be repaired, they have to be replaced.
What is the make and model number of the washer?