Hello, I am an environmental engineer sharing my design for a ~300 gallon IBC tote rainwater collection system. What makes this different and beneficial for self-sufficiency is the low cost per gallon. This tote also provides a large enough storage tank to use a dedicated irrigation pump for reuse. You could make this as simple or as complex as you wanted to.

IBC totes are frequently used for storing and transporting food grade materials, so there is an aftermarket for cheap used totes, you just have to verify what they were used for. I got this 275 gallon tote off of marketplace for $100 USD. It was previously used to transport food dye. They are highly durable because they're built out of HDPE and galvanized steel.

Other Materials:

Leaf filter, from $10 to $70 - my preference is the Leaf Eater Advanced ($66)

Downspout diverter, my preference is Earth minded Flexifit diverter ($20)

PVC pipe and valves, figure $50

Total entry cost including tank: $180 - $240

Optional:

Lid adapter for two inlet ports $10

1 HP irrigation pump $140

Discharge splitter $10

Wi-Fi controller $30

Piggy-back Level float, alternative controller $50

Ozone injector to keep the water fresh and odor free: $400 (luxury) JED Engineering model 203

Check your local regulations also. In some localities, diverting and collecting rainwater is not legal. Some places where it isn’t legal have exceptions for irrigation though.

Just be aware before spending a lot of time and money on a project.

And these laws are FUCKING RIDICULOUS.

Isn't that normally for water that has landed on the ground rather than on your own roof? What if you just dug some trenches to collect the rainwater in the land it just happens to collect in a pond

Maryland had talked about making our illegal to collect any rainwater, be it from your roof or anywhere else. I no longer live there so I never kept up with it.

ETA: looks like Maryland did not impose restrictions on rainwater collection after allon. And Montgomery County offers incentives.

In New Mexico both Albuquerque and Santa Fe offer incentives.

https://worldwaterreserve.com/is-it-illegal-to-collect-rainwater/

I found a site that lists used tanks. https://ibctoterecycling.com//used-ibc-containers-for-sale/

What would one use 300 gallons of rainwater for?
I'm not trying to sound judgemental or whatever, I'm actually curious because 300 sounds like a lot.
Is it mainly for irrigation? Would that make sense for a larger garden?
I've heard that some people use graywater for flushing toilets, is this part of that?

It's just water bro. Shower, laundry, drink it, whatever. I have a thousand gallon tank, nice family home might have 10k. No other water source

Thanks for the shopping list. I'm in the early thinking/planning stages for a rain water collection system at my own house. Love seeing what other people are doing.

When there isn't much rain in the summer and you try to keep your plants alive with collected rainwater, I assure you that it empties fast

Which controller are you using for your setup? Any reason in particular?

I'm wondering if I should set up a misting nozzle for mine and if I'd need a pump for it.

Where did you get the cover?

I am not the OP, but even if it doesn't have practical use, I just think this is coolest thing ever. It also aligns with self-sufficiency and resilience values of this solarpunk server

I am not collecting the water, it just happens to have flooded that part of my garden. "Land of the free" and you can't even leave an open container outside if its raining?

Usually they are there to make sure the (storm water or mixed) sewerage systems get properly flushed. It's not as ridiculous as it sounds at first.

Tbh even my fairly small garden could make use of this much water in the UK. I focused on keep stuff alive rather than optimal growing conditions.

Problem I find is that collecting rainwater is difficult to justify on the price of it. I looked at tanks out of curiosity, but water is so cheap that it could never realistically pay for its self.

Space is also difficult as my garden is fairly small. Looked at underground tanks but the prices there are even more crazy. I think the most cost effective option for me would be to just dump greywater on the garden instead. That just costs a pipe. Maybe something to put over the pipe where it crosses the path to avoid a trip hazard.

so its like a bag? like does it inflate with water and then deflate as you use it or is it rigid?

No it is rigid. Just search for "IBC container" and you will see how it looks under that cover. Those tanks are widely used to transport liquids.

I understand some of the reasoning behind it, but it doesn't logically make much sense in the end, as if you collect rainwater, you're eventually going to return it later...

The water cycle ends with me.

I can't figure out what you mean.

And yet they allow corporations to relentlessly pillage all water sources going 2-3x their paid water rights while the populations eat the costs and effects...

It is all excuses to increase water insecurity.

You can also buy IBCs with galvanised sides, which is pretty cool.
They can be £10-20 more expensive, but makes the whole thing more robust, in my opinion.

Eg: https://smithsofthedean.co.uk/product/ibc-tank-1000-litre-galvanized/

Ours have little holes drilled in the front side every 100l to expose the plastic tank underneath, so you can see the liquid level.

I would recommend this type so you don't need a separate cover, which could get ripped etc.

It would be good to know which wifi controller and "alternative controller" you are planning to use.
I'm after one, but so far, most of them I have seen need crappy apps. I want mine to use an open API etc.

Our UK garden is about 75x75m, which is a decent size, but not massive.
About half to 3/4 of it is grass, which I hardly ever water, and haven't this year even though we had a drought.

We have 5 IBCs, and several other randomly-sized water butts (~7000l total (1500gal UK, 1850gal US)), to keep our veggies and fruit bushes watered. We ran out this summer, and had to use about 500l of tap water until it rained again :(

Dry periods are likely to get worse in future, so I need to get more water storage.
I also want to start using rain water to wash clothes (or at least fabrics we use for our pet rabbit houses), but I need a good filtering system first.

We have 2 IBCs stacked, and I was trying to use the top one to gravity-feed our downstairs toilet cistern for flushing and worked well, although it took 7 minutes for the cistern to fill, which isn't great if you have to accommodate a lot of people.
It is good enough for us though.

I could add a pump to speed up the process, but I'm trying not to add more cost and complications to the system unnecessarily.

I can fit 1 more IBC in somewhere - they don't look pretty, but they are very practical.
I normally transport them home on the top of my car on a roof-rack.... and drive slowly! :)

Those look nice, but I have already got two tanks...

Usually they are there to make sure the (storm water or mixed) sewerage systems get properly flushed

I think that might be mostly from inherited old regulations/infrastructure, as most modern policies revolve around having separate storm water and sewage system for the opposite reason, as they don't want all the extra rain water overflowing the sewage treatment systems

Fair enough, and with underground tanks you need a way of getting the water out again, which usually means pumps, which adds expense and maintenance, and you have to make sure the water is really clean.

Using greywater is sensible. Switch your soaps to nature-safe ones to help - https://www.faithinnature.co.uk/ make some good hand, shampoo and dish-washing soaps.
I really like the solid shampoo bars from here: https://www.soapnuts.co.uk/products/bulk-mixed-shampoo-selection too.

You can also get filters to help get rid of the impurities.
One system is using a reed bed if you have space: https://www.reedbeds.co.uk/

https://www.hockertonhousingproject.org.uk/ has such a system as part of their pond system. We went on one of their open days a few years ago, which was really interesting.

Reed beds are an interesting idea, I had initially thought of having it poured directly into an earth channel or two along my garden so it soaks in almost immediately and avoids having any standing water as I had heard storing greywater can rapidly get unpleasant. I suppose as long as it is filtering more than it goes stagnant then it should be alright.

Collecting it should be ok, got 2 pipes going out the house, one from the bathroom and other kitchen and they are next to each other. I think bathroom (not toilet, that is separate) is probably cleaner and contains less soap. Realistically it would only be necessary during times of drought anyway, now we are going into autumn there is already enough water from rain. Which should also help flush out anything that could build up from the greywater.

Sounds good. Yes, I wouldn't want to use toilet water, but bath and shower water would be ok. Just remember when you're cleaning the bath with bleach or similar, send that water back to the normal drain!

Kitchen water from washing up should be fine, just watch that you don't put too many fats down the drain, as it could smell and attract rats etc, possibly (just guessing, but I would think it would be a bad idea).

Also, i guess you need to think about the temperature - you don't want hot water near your plants!

Next year I should think about doing the same thing with shower/bath water at least, that is probably the cleanest waste water.

If you just want to use an earth channel or similar, maybe have a look at "Field Drains", eg: https://store.jdpipes.co.uk/land-drainage/ ? although you might have to get access to them now and again to clear the holes.

To be fair excess fats are bad for the normal drain too. Temperature is a good point, my initial idea was that the channels would be along the grass paths so if a bit of grass dies by the opening it isn't really a massive concern. By the time it soaks in any real distance it should be cooled by the surrounding soil.

Bath/shower usually is the cleanest source to go for first, the pipes are next to each other for me. Either way I would set it up so that they can be easily removed when I don't need the water going onto the garden.

Do need to check how flat the area is, exit point from my house is pretty close to the ground so a slight elevation change could be a problem.