Still having trouble with leaking behind washing machine even though shutoff valves now are fixed! This time it's from the hoses. These hoses were installed new about two years ago, probably haven't been used five times so are in great shape. The leaking is coming from the filter washers in the couplings--the kind that look like garden hose washers with a screen inside--apparently from taking off and reattaching the hoses while working on the shutoffs. The "rubber" couldn't bear the crushing since the washers are molded around wire screens hence do not have as much rubber as a plain washer. The question I need answered is: Can I double the washers to overcome how much they've been crushed...you know, by adding a plain washer on top of the filter washers? I think that's probably a no-no, so am I doing something else wrong?

How many times they "Have been used" has absolutely nothing to do with the longevity of the hoses. Why not just replace the screen washers?

If it where me I would just replace the hoses. The number one cause for water damage in a house is a failed washing machine hose.

Hoses should be replaced every 5 years to avoid bursting/flooding.

In a pinch, I am sure you can double up the washers. But I would not trust this connection for an extended time, as the extra washer could slip loose and start leaking.