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Rainwater Filter


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#1 PeterW

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Posted 13 July 2015 - 01:57 PM

Afternoon

Anyone know of a good source of rainwater filters - preferably fairly fine - for use in a DIY harvesting system..?

Looking to see how we can remove as much fine stuff as well as leaves etc, most of the big harvesting companies don't sell the bits of their system as single items and I don't really feel like doing some magic DIY on this one..!

Cheers

Peter

#2 tonyshouse

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Posted 13 July 2015 - 03:50 PM

Gravity works well in mine, all the silts and heavy stuff finish up in the catch pit or in the bottom of my holding tank, a tiny bits of very fine stuff gets through into the cisterns, I have a stainless gauze filter but there has never been anything in it, if it doesn't float or sink it seems not to get through my pump in big bits.



#3 HerbJ

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Posted 13 July 2015 - 04:59 PM

In fact many of the RWH companies do sell all the elements separately - see http://www.rainwaterharvesting.co.uk/rainwater-harvesting-filters/7/.
This are good basic filters.

If you want a better filter ( more expensive) - see http://www.rainharve...roducts/filters

#4 jsharris

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Posted 13 July 2015 - 06:03 PM

It's pretty easy to put together a custom DIY filter system, but you need to know what you're trying to filter out and have an idea of the sort of water quality you want to get out (in terms of freedom from bacteria, cysts, level of turbidity, dissolved stuff from roof covering, pipings etc and stuff that is a consequence of some treatment systems (for example a lot of chlorination treatments leave behind chloramines, which aren't nice).

What do you want to use the rainwater for? That's a good starting point, as it sets a baseline for what a filtration system has to deal with.

At the most fundamental level, I'd start with fitting hedgehogs to the gutters, if collecting water from a roof, as they will keep all the leaves and big debris out and need no maintenance (they keep your gutters clear, too).

After that it's wholly dependent on what you want to use the water for - if it's just for flushing toilets then only basic treatment is needed, enough to give clear water that is free from nasties like psittacosis (common in bird poo and can be easily released as an aerosol when a toilet is flushed, so infecting people by inhalation). If it's for washing clothes, then treatment needs to be a bit more thorough, as youll want to filter out or other wise kill cysts as well as bacteria, and may also need something to get at the most common viral particles.

On the other hand, if all you want to do is water the garden, then you need next to nothing in the way of clever filtering and treatment, just something to allow settling to take place and then allow natural algae to keep the water clean and safe for watering.

I've probably (and wholly accidentally) acquired more information of filtration and water treatment than most will ever need, as a consequence of finding the optimum way to treat our borehole water. In fact I found a new phenomenon today, when I decided to disinfect the borehole as the lid didn't fit well and I'd had a pipe down there to try an aeration experiment, which found another batch of orange iron reducing bacteria growing in there. I shock chlorinated the borehole, but used a different brand of chlorine shock granules. Somehow I've pushed a few hundred litres of water in the borehole up from a pH of 7.4 to a pH or 10.5, with virtually no free chlorine and lots of milky white precipitate, even after pumping around for a couple of hours. It looks like I shall have to pour some acid down tomorrow to lower the pH and release the chlorine to do it's job. I'm guess the pool chock granules I used must be a lot higher concentration than the last lot. Still, we learn from experience.

#5 PeterW

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Posted 13 July 2015 - 06:48 PM

Thanks all

I resent paying £270 for what is in effect 3 plastic mouldings and a bit of stainless gauze.....!

Erring towards just using it for "outside" water such as car washing and watering. May even be just 3 IBCs buried at the moment but working out the plans

Cheers

Peter



#6 jsharris

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Posted 13 July 2015 - 07:17 PM

If just for non-critical stuff like this then buried IBCs are perfect (and cheap). Fit hedgehogs to keep the worst of the crap out of the downpipes, that removes 90% of the need for fancy leaf filters etc. Then fit diverters to the down pipes to redirect water to the IBCs, allowing water to flow to the soakaways when the IBCs are full.

Couple the IBCs to each other at the bottom and fit manholes over the top opening of each so you can get at them to suck out sediment periodically. Fit a submersible pump in one (a cheap one with no float switch will work fine) and wire it via gland in the tank and a length of SWA cable fitted to a watertight underground junction box. Terminate the SWA in a consumer unit with an RCBO for both over-current and earth fault protection.

You can switch the pump manually, but the neatest way to do it is to fit a tap with a flow switch (suitably rated for the pump). This way turning the tap on starts the pump, turning it off stops the pump, with no need for any fancy stuff.

The best supplier of this stuff is Smiths of the Forest of Dean. They not only stock loads of stuff at a good price, but have a wealth of knowledge on how to fit it all together. Should be an easy DIY job - yell on here if you have any problems.

Edited by jsharris, 13 July 2015 - 07:18 PM.


#7 PeterW

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Posted 13 July 2015 - 07:32 PM

Thanks Jeremy !

#8 bitpipe

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Posted 13 July 2015 - 08:55 PM

I'm also looking at a rainwater harvesting system, just for flushing loos and garden use - doubt I'd extend this to laundry use.

To allow for emergency egress from our basement, we're building an external stairwell which will have additional space to house IBCs so makes sense to use that vs a buried tank which takes us into the DIY realm so very interested in what you plan to do.

One note, if using RWH for any internal use, thought also needs to be given what to do in times of low raid (likely in the SE) and power cuts (less likely). The site that Herb references has solutions that legally enable mains top up and also have gravity systems that get past the power cut issue.

Also, you need to ensure that only roof water is harvested and that surface water (via ACOs or similar) has a separate run to a soak-away as this would be much dirtier and potentially more contaminated.

Edited by bitpipe, 13 July 2015 - 08:58 PM.


#9 jsharris

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Posted 13 July 2015 - 09:15 PM

Loo flushing needs a degree of sterilisation, depending on where you are. If you get pigeons anywhere near your roof, then you almost certainly need to use some form of sterilisation to kill psittacosis, as that is rife in pigeon poo and can cause serious illness if ingested. It might sound odd to think of a loo as a source of ingested stuff, but flushing puts an aerosol of flush water into the air around the loo (a good reason to close the lid before flushing) and if the water contains psittacosis washed off the pigeon @!## on the roof then you really want to get rid of it.

The snag is that for UV sterilisation to work you need UV on 24 hours a day (at around 30 W), you need filtering down to a least 5 microns to ensure that the UV sterilisation works (otherwise bacteria can hide behind particles and miss getting irradiated) and a 5 micron filter will clog very quickly unless there are pre-filters to take out the bigger stuff.

All these filters cost money to replace every few months (and they are not cheap), so I've been looking at filters with a higher capital cost but no running cost. There are filter media available (zeolite based, like Micro-Z and Turbidex) that filter to the sub-5 micron level. You can then use something like a Doulton Rio 2000 filter to get virtually sterile and water that is safe to drink at the output, at a good enough flow rate for a tap (10l/min or more). The pre-filter needs backwashing every few days, when the pressure dops, but tht can be automated for a couple of hundred pounds, or you can take the cheap option of just operating a valve when it's needed. The ceramic filters in teh Doulton will last a long time if the pre-filter is good and they are cleaned every few months with the brush provided.

Might be an option for those in high rainfall areas as a back up water supply, especially if you live in an area where water is expensive. None of this stuff is hard to put together, you just need to know how to pick the right components and where to get them at a reasonable price. Sadly some of the stuff is costly here, as it nearly all comes from the US.

#10 bitpipe

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Posted 13 July 2015 - 09:24 PM

Interesting Jeremy - I've not seen any reference to treatment to water for flushing loos beyond basic filtration on any of these systems.

#11 mafaldina

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Posted 13 July 2015 - 10:01 PM

The rainwater I collect (lots I live in cornwall, three buildings average 90x20m each) I use for cattle/poultry water. Admittedly i have no overhanging trees, I use a (clean) old bit if a pair of tights over end and empty if clugged, which is not very often. To discourage deer, well worn same tights with hair from hairbrush in.

#12 jsharris

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Posted 13 July 2015 - 10:11 PM

View Postbitpipe, on 13 July 2015 - 09:24 PM, said:

Interesting Jeremy - I've not seen any reference to treatment to water for flushing loos beyond basic filtration on any of these systems.

I think it largely depends where you are. We get a lot of pigeons/collared doves crapping on the roof, so are acutely aware of the problem. Similarly in Cornwall we had the usual problem of gulls crapping on the roof. Messier, but probably not as harmful to health as pigeon @!##.

A lot of people don't have these problems, or choose to ignore them. Psittacosis is nasty enough for me to want to take avoiding action, although I only became aware of it as a risk when working in London and we were given a briefing on the health risks from pigeons and why there was a big programme of work on to stop them roosting on the roof and ledges around the building, together with instructions to staff to no feed them outside.

#13 DH202020

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Posted 14 July 2015 - 06:11 PM

Interesting, I have not as yet seen any additional information on advertising leaflets regarding 'bugs' in water from the water harvesting tank suppliers, they recommend using rain water for flushing and washing machine!!

With that in mind, would bromine tablets work if placed in tank?
They are recommended for hot tub use, if so how many would you need for say 3000ltr underground tank? Would they effect watering the plants in the garden?

#14 jsharris

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Posted 14 July 2015 - 07:24 PM

If you can avoid using chlorine or bromine do, as managing the pH so that they actually work and so that residuals are minimised isn't easy.

The bugs in rainwater problem is pretty obvious and I'm amazed that it is ignored. A look at any roof will show that it has usually got a LOT of "faecal matter" all over it, and that ends up in the rainwater tank. I think some people have some sort of psychological block that stops them realising this.

The best way to kill the bugs without introducing any chemicals into the water is to use UV. A UV steriliser does need a clean water feed, as any turbidity will stop the UV penetrating, but if you cvan pull off crystal clear rainwater from a tank that should be fine. The UV tube also only needs to be turned on when you're using water, so needn't cost a lot to run, plus the tubes will last a long time when used like this (tube life is typically around 10,000 hours, hence the recommendation to change them annually in a whole house system that's one 24/7)

#15 DH202020

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Posted 15 July 2015 - 08:26 AM

This is a reply from a well known RWH company in regards to bugs in water...

"collecting rainwater off
of the roof will of course pick up the odd amount of contamination,
however, if it gets into the underground tank and once it has been diluted within the quantity of water held in the tank and bearing in mind you are also drawing water from about 4 - 6 inches up from the
base of the tank no sterilisation is needed, this is the same for
washing machines."

Any thoughts on the above?

#16 jsharris

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Posted 15 July 2015 - 08:50 AM

Once you have faecal coliform bacteria in a water supply they will stay there and feed on whatever organic matter gets into the tank. They won't go away, settle to the bottom, magically not get sucked up the intake pipe or whatever, they will do what bacteria are good at, and breed. The will breed more slowly in an underground tank, where the oxygen levels may be lower and where the water will be cooler, but they are very tough and hardy bacteria and they will survive and breed.

The won't be killed in a washing machine, either, as all washing machines now cold rinse, so the last water anything in the washing machine will be in contact with will be contaminated with coliforms. BTW, coliforms are generally not too bad, but some of the escheri coliforms can be fairly nasty (these are often abbreviated to E Coli by the media).

To put this in perspective, coliforms of all types are very common and in soil everywhere, largely because creatures of all sorts excrete them everywhere. Only some coliforms are harmful to people, and of those that are most will only ever cause something like a mild upset stomach (an awful lot of minor forms of "food poisoning" is down to coliform contamination). If you are bothered, then get a simple coliform test kit, follow the instructions carefully (and I'd add that it's worth washing the outside of the top of the sample bottle and your hands with some alcohol to avoid a false positive) and check. The test is easy, takes about 24 hours in a fairly warm place and gives a very clear indication of total coliform contamination. You can buy the test kits here: http://www.simplexhe...test-p-286.html but it will ALWAYS give a positive result on stored rainwater. There are more specific test kits that will only respond to the more harmful coliforms, like E Coli, but they tend to be more expensive, and again you can be pretty certain you are going to have E. Coli in collected rainwater.

It's up to individuals to make their own mind up as to what they want to do. For thousands of years we used collected rainwater for washing and drinking. Thousands of people got ill, but we never really worried about it. Many developed resistance to water-borne bacteria, too, having been exposed to it all their lives.

Would I want to sleep with sheets against my face with bird @!## bacteria on them? Personally I wouldn't, but others may well take a less fussy view.

#17 Richard111

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Posted 02 April 2016 - 02:19 PM

Interesting comments. I harvest rainwater into four 1,000 kilo tanks. I use the water for toilet flushing and the wife waters the garden as required. Did have problems in the early days with the stop @!## valves getting clogged. Resolved this with my home made filter. A short section, about 3 inches long, of 2 inch diameter plastic water pipe plugged into the 1 inch down pipe. The piece of 2 inch pipe was stuffed with discs cut from clean scouring pads. I use four discs. They must fit the pipe diameter firmly so as not to tilt when water flows. System been in use for over five years without any problems.
Main outlet is 6 inches up from bottom of second tank. Two tanks are connected together about 6 inches from bottom. Water inlet from gutters into first tank which collects most of the heavy crap. Drain and pressure wash tanks to remove sludge and then top up from other two tanks. Takes about two hours on a nice sunny afternoon. Wife now has limited water until next rains. Not a problem these days. :)