Simple questions about components

Hi, I've build one IBC tote using internet purchased components but want to add three more.  The components on the internet are pricey and I have some questions.  Some important info about my site is I live in Dry Colordo at 7500':

1. Why do downspout diverters have such a big opening?  Doesn't this loose some of the water?  At my location I want to keep every last drop.

2.  Does anyone have DIY filters for removing debris before the water enters the tank?

3.  I was thinking about directing my downspout straight into the tank to capture everything and placing the filter before it.  I figure there should be a simple DIY solution for the filter out there.  For overflow I don't see what's wrong with allowing the overflow to simply come out the top where the water enters or through an overflow pipe coming out the IBC tote so long as this overflow is directed downhill away from my home.  Am I missing something?

Hi S.
Are you talking about a first flush diverter? If so, I would highly recommend it, even if it wastes a little water. If you meant something else, I am not sure which piece you mean. Also, what will this water be used for? If you have the first flush diverter and it is for garden or livestock... then all you will need to do is keep the algea from growing and probably wouldn't need any other filter than the first flush. If you intend to drink it yourself, then you would probably need some really good filter, but I would suggest filtering it after storage personally. Maybe something like a Berke, although I have seen people make their own sand filters that seem to work pretty well.  

We use a piece of wire mesh to keep debris out of our tank.

Our rainwater goes from the gutter thru the first flush diverter and into the tank via a PVC pipe.

I can understand the desire to capture every drop. Are you usually on site to move spouts around, or do you want a set-and-forget system? Connections and piping for gravity feed setups can be creatively scrounged and improvised -- a "complete system" from an online retailer will be much more expensive.

When you consider the bird poop, rodent poop, bat poop, and other pathogen-bearing deposits from wild animals that accumulate on a roof, a flush diverter makes sense. It also reduces the load of fertilizer coming into your storage tanks, which otherwise would feed algae blooms.

There's nothing wrong with capturing and using the flush water in a barrel and using it elsewhere. I just do this manually. An open top barrel is much easier to clean out than an IBC tote.

With our IBC totes I use a 3"x4" PVC adapter with a screen mesh attached to it.

Regarding the first flush I have incorporated them in all my systems but I'm sure have effective they are. Sometimes, we'll have a light drizzle that fills up the first flush volume followed by a downpour that probably really knocks loose all the stuff that was supposed to go into the first flush.

I like having a valve so if we lots of rainfall over a short period I can bypass the first flush.

Thanks to everyone for your response. And thanks for those pictures of your screen filter!  Very helpful.

This is for garden use and tree watering only.  I have completely painted these totes along with a thick coat of primer. I then have wrapped them in black poly. So far it’s kept the algae away in my first tank (after the painful lesson of algae).

I currently do not have a first flush system. I can see how they’re useful but am focusing cost and time on getting my additional tanks up and running.  If others feel very strongly I will reevaluate but as someone else pointed out, I have some skepticism on their efficiency.