This post is all about fitting a homemade rainwater harvesting system. My last post discussed the availability of rainwater and how you can evaluate this for your needs and make rainwater work for you. I recommend using a blue barrel with a clamp on lid as a storage tank as the clamp will come in handy to fit the water filters. (but you can use any tank you like, appropriate to the level of rainfall you are expecting to store). Note that storing water for a long time may give you problems due to the attraction of bugs and bacteria (particularly for hotter countries). You may wish to dose your water with chemicals to avoid this. See the following image, click and zoom for details.
heres some pictures of that blue barrel I recommend, these are popular with canoeists:
Note that I say "adapted" fresh water inlet valve in the diagram, this means you will have to adjust the float arm length or position until you are happy that it refills with normal (network supply) water to the right minimum level. Something like THIS plus a ball float valve. You may have to extend the arm, use a brass or plastic rod for this, something that won't rust or decay underwater.
Power shower PUMP --you need something that will provide some pressure to deliver water towards the washing machine, particularly when the rainwater tank is nearly empty.
To collect rainwater from the roof, note that the water will swirl around on the inner surface of the rainwater down pipe coming down from the roof. Therefore for capturing this, an inner edge that encourages water towards the opening mouth of your feeder tube (towards the storage tank) can increase the efficiency of collection. Also it is a good idea to have an overflow pipe flowing down at an angle from near the top of the storage tank, back to the rainwater down pipe. This stops excess water spilling over the top of the tank
Water draining away from the washing machine could be collected for reuse -but I'll save that for a separate post, see here for rainwater to washing machine page