First flush really necessary?

I keep seeing people setting up a first flush diverter on their rain water catchment system. I understand the concept as to why it is done but all the video and article I have seen simply release the first flush into their garden or swale between rain. If that is the case, why bother putting a first flush to begin with?

Thanks,
Kris

Kris Minto wrote:I keep seeing people setting up a first flush diverter on their rain water catchment system. I understand the concept as to why it is done but all the video and article I have seen simply release the first flush into their garden or swale between rain. If that is the case, why bother putting a first flush to begin with?

Thanks,
Kris

We catch everything we can....no 'first flush'. Sometimes our rains are so rare I don't want to miss a drop and sometimes our rains are so frequent we could not keep up with a diversion...and like you say it is still going into the soil somewhere. It is one of the very few compomises I am willing to make...we have a thirty five year old shingle roof. I wonder if some drain the 'first flush into a septic systom? We don't have one and that would, I think, just pass on the problem.

I did not put a first flush system because the water would end up in my soil unless I dumped into the city water treatment system which isn't very permaculture. The amount of energy and chemical used to clean our water is pretty enormous.

Kris Minto :I am going to talk about assumptions, and "I think that"(s), but its o.k., I dont charge for any advice I give Here ! 1st assumption, if you are collecting rain water
you have Very Hard Water, or not much of it, a 'low water table!' My comments relate mostly to the history of the Water Rich climate of the Northern states east of the
Mississippi.

At one time the silo that stood next to the Barn might be pressed into use through the late spring and summer as an additional cistern to hold rainwater, Hard water will not
clean up milking equipment / and station (milk) cans as well as soft rain water, diverting the first charge of water allowed old bird poop, lichen,moss, algae and the little bits of
wood they had been cemented to on the barn roof to be flushed away !

In the farm house basement a cistern would be laid-up directly under the farm house Kitchen. again Soft rain water was a highly regarded treasure for cooking and wash water!
the first flush of water of of the farm house roof was diverted for the same reasons, the rest going into the Cistern !

So there is a Historical reason for a first flush - the actual question is what is being done with the rest of the Rain Water after the 1st Flush ! Hope this helps Big AL !

Kris Minto wrote:I keep seeing people setting up a first flush diverter on their rain water catchment system. I understand the concept as to why it is done but all the video and article I have seen simply release the first flush into their garden or swale between rain. If that is the case, why bother putting a first flush to begin with?

Thanks,
Kris

So you don't have to drink it! For a garden-only tank, it does help the water stay "fresh" in the tank longer.

The bird poo and dirt from the roof can cause things to grow in the water--they may or may not be bad things for you or the plants, but most of them plug up sprinklers and soaker hoses real quick.

Thanks for your response Allen. What you wrote make sense but that likely doesn't apply to 99% of individuals now days. I get the impression people are simply following a template seen in book or online and not asking themselves the question "what purpose will this serve me?". Using more material to create a first flush when there is no added benefit isn't very environmentally friendly and adds more complexity to a system which can result in more points of failure.

I have a small rain catchment system but did not install a first flush because the water would simply be dumped in my garden where the rest of the water in the tanks will be used for.


Thanks,
Kris

R Scott wrote:The bird poo and dirt from the roof can cause things to grow in the water

Poo and other things with pathogens in them are pretty much the only reasons I've heard of for diverters in NZ.
I'm generally not worried about that kind of stuff, but if you have a dry period, then a downpour, it can was a lot of crap into the tank
There's so many variables, like are there young kids or immune-compromised people using the water?
What's the bird/squirrel/possum/rat population like?
And so on.
I holiday with some people who don't have a diverter and there's a lot of wildlife pooing on the roof.
I always get a bit of a dodgy tummy, but theirs must be used to it!
I'd divert it into a garden barrel.

Leila Rich wrote:I'd divert it into a garden barrel.

I am assuming you then use that water onto your garden. If so I don't see how using a first flush if of any use. The only reason I could come up with why I personally would use a first flush is if I was using the water for an outdoor shower/sink.

I think the point I am getting at is 90% of individual who use the rainwater catchment system is to water their garden then I don't the real benefit since the first flush still ends up in your garden one way or another.

Thanks,
Kris

Kris, I think I'm misunderstanding. You want the rainwater catchment for drinking, right?
If it's just for watering, that's another story, and R Scott makes good points about that.
I can only speak for local conditions, but here basically all roof-collected water is drinking water, hence the first flush to get rid of pathogens. The volume of water 'lost' is pretty tiny and considering it can be used on the garden, no water is wasted anyway.

I live in the suburbs so I don't drink my water, I simply use it for my garden. I think the issue I have is all the books, video and articles I've read need to explain when you should install a first flush and not just advise everyone to follow a template. As I stated above, most individuals wouldn't need one which would save on cost and waste.

The only reason I came up with having a first flush for those who are only planning to water their garden would be to remove any contaminants and divert it to a spot on their land which isn't being used for some type of food production. This isn't mentioned in any of the material I have read. In my case that's not possible because I live in the suburbs and utilize my whole 1/12th of an acre for growing food.

Kris

Iam with R scott on this mainly because of my situation. I gravity feed, drip irrigate directly from my tank and have problems with the bottom outlet of the tank being clogged and the pre-drip irrigation filter becoming clogged. This is WITH a first flush diverter. Iam adding a screen to the system after the diverter to further reduce the debris getting into my tank. Probably start a new thread to show it off soon.

R have a first flush, installed to reduce the debris coming of off my ancient asphalt shingles.
It doesn't seem to work so well.
My tank is darkened with deposits up to the water line. I am planning to cut open the top and pressure wash it then add a furnace filter inline.

I live off of catchment water. I do not have a first flush divertor on our system because our rain often comes in small amounts, 0.1 to 0.2 inches at a time, although we will have bigger rains intermittently. Especially during drought years, we want to catch every drop for the house use.

I do not drink our catchment water because we have close and easy access to excellent, free, county provided drinking/cooking water. But we use it for all other household use.

We use a coarse cloth filter to catch most of the debris as the water enters the storage tank. But it doesn't catch everything, especially the fine volcanic dust. And of course any bird, bug, or rat poo enters the water though the coarse solids are trapped by the cloth filter. Therefore we treat the water with baking soda (to adjust pH) and bleach in order to make it reasonably safe to use. As for fine debris, it settles to the bottom. We clean the tank every few years as needed. In 10 years we only cleaned the tank once. We keep a tarp cover over the household water tanks. Our water is not drawn from the very bottom, so there is less chance of sucking up the debris.

First flush divertors make sense, in my mind, if one gets enough rain. But if rain is scarce, then every drop counts. If I were to use a first flush divertor, then I'd definitely save that water for garden use.

We have a leaf eater. You don't want to clog your tank with rubbish. Given the quality of most town water these days I would always want to be able to drink the rain water. But for that it is more important to clear the gutters every now and then.