Rain water tastes delicious (a few minerals missing but hey!) and is free.

Even if you run the mother of all watermakers, you may still want to consider a way of harvesting this delicious free resource.

On Caramor catching rain water is an important job and although we can fill our tank during a heavy downpour, we would be keen to improve our system. We would love to hear your ideas and learn about your designs.

Caramor’s system:

A shade tarp with a hole in it. In the hole we have fitted the best piece of plumbing we could find, with a hose attached to it that feeds into a jerrycan. Once full we pour the jerrycan into the tank.

Downsides: we can’t use it underway, only a small area of our tarp is actually contributing, someone has to be on hand to empty the jerrycan.

Hi Kath and everyone,
It is nice to see a “how-to” article on an important subject and a photo essay to boot. Watermakers do crap out, need power and are expensive and we all know that many did impressive cruising without them. Tarps are a time-honored way of collecting water and work well, but do have small hassles which you speak to. Every widely wandering boat is wise to give some thought to this subject ahead of time.
Another alternative: some, maybe many, boats can use their whole deck for water collection which impressively speeds up the filling. The boat requirements are a bit of a deck edge raised portion, height is nice but not necessary, just a raised edge. Then the fresh water fill thru-decks must be on the deck and the closer they are to the lowest part of the deck the better.
Then the scuppers must be blocked. Mine are through-deck and I was able to lay a piece of rubber, cut to size, over the scupper grate and on top of that place my lead shot dive weight bags. Others will have to improvise: the wide 3M blue and green tape will do for this job and are easy to remove and leave no adhesive,
If able to anticipate the rain, cleaning the deck allows for water to be taken in immediately, pay attention to bird droppings which I consider the only truly objectionable deck ornament. If not allow the rain a few minutes to wash salt off and then close the scuppers and open the deck fill.
I played with a screen over the deck fill for few rain fills to catch debris, but in the end found them un-necessary. If your fill holes are on the higher side of the deck, sometimes water can be channeled/directed without too much trouble.
It is impressive how quickly one can get full tanks when the whole deck area is your collection basin.
My best, Dick Stevenson, s/v Alchemy

Here's my take on the raincatcher:

For my first tries, I used a tarp. I found that although it was a fairly heavy one, it would billow and shed the water, as rain and wind commonly come together, in a squall or when a front passes. Also, the surface was too close to horizontal, so in a light shower, the water drops would stay on the surface and evaporate, rather than running down to be collected.

So, I got some heavy PVC cloth, 16oz/sq yd. I made an 'L' shape with long sides 2metres, short sides 1 metre (imagine a 2 metre square, then remove a quarter of it, a square of 1metre). Then I sewed the short inner sides of the 'L' together, so that I ended up with a funnel with a equilateral triangular top, with sides of 2 metres. The seams are then waterproofed with something compatible with PVC, and a half-inch plastic skin fitting is sealed into the apex of the funnel. A short piece of half-inch hose leads to a 10 litre container (to inspect the contents before pouring into the tank). The top is hemmed, and grommets and short lines are added at the corners.

This worked pretty well, both underway and at anchor, rigged over the cockpit, as some depth is needed. Two of the lines are made fast to the top guard wire, and then the funnel will fold flat against the guardwires or cockpit side until deployed. It will also fold into a neat flat package for stowing below. When rain looks like arriving, it is the work of a moment to tie the third line to the guardwire on the other side. Each time that I went through the doldrums, I could guarantee to come out the other side with full tanks.

Watermakers? who needs 'em?

By the way, this kind of triangular funnel is a good way of making drogue cones.

From one who has been there done that.  
https://atomvoyages.com/articles/improvement-projects/251-rainwater-1.html

We have a watermaker but also a raincatcher. The latter is a pvc sheet deployed on the foredeck and attached to the guardwires.  It has a hosepipe connector at the lowest point, which is also tied down to the deck to stop flapping.  We let rain run to clean and then run a hose to the tank deck fill.  
The main problem is we  often get our timing wrong and are late deploying it. Having the watermaker reduces the incentive to use it.