three-way valve

Of all the steps we've covered so far in this series of videos on pond installation, this is the only one that might be considered atypical, basically because the need for completing this operation depends on the type of filtration system you're using.   In this case, we're installing a permanent gravel bed in the waterfall/filter unit, which means we need to include a backwash system in the form of a three-way valve and a drain line to make the bed easy to clean, refresh and maintain.  The great thing is