"Greywater" is water that comes from your sink, shower, bathtub or washing machine. It's not drinkable, but it's still usable. You can water plants with it, or even install a "greywater system" to filter and reuse the water in your toilet tank.
Available for free or cheap at all home improvement stores, PVC pipe is totally great for home storage and organization in different ways. Take a look at these DIY PVC pipe storage ideas for inspiration.