Advice Sought on Simple IBC Rainwater Harvesting System

[Pilgrim]

I'm planning a simple IBC rainwater harvesting system and would appreciate a little advice. We have a flatish roof, which is just about enough headroom to drain into a tank in the attic in the north corner of our building. I'd like to set up a simple system to feed our toilets and washing machine. I don't want to spend too much as I want to make sure that I can keep the water cool enough. The burning questions:
- is there a way of building a cheap filter that does not take up too much vertical space as there isn't much?
- is there an easy way of adding a stopcock to keep some water in the tank from the mains when demand is high?

Any comments would be very much appreciated!

[MR GUS]

You need to read up some threads from that area, as pretty much every aspect will have been covered over the years.

Have you understood the area lading of the roof  (trusses) & taken appropriate measures?

Have you read water / plumbing regs with regards to  back flow (etc).

Have you seen the thread with the commercial "in roof" diverter as a pre-engineered option on harvesting in a low profile manner, its all there as resources, based on others professional / bodgineered set up.

Your problem is likely grey water / potable inlet (badly put, as I'm no plumber) & potential for contamination via back flow which is why keeping the two separate is / was the route of many. ..since some of those earlier posts there are other options.

You calculated the viable run off as a first step?

[Countrypaul]

You don't say anything about the rafters used for the ceiling/floor of the attic, but you need to bear in mind that a full IBC will weigh around 1 tonne - so some reinforcement of the platform you intend to use may be required.

As Mr GUS said if ou want to top the IBC up with potable water you must have an air gap between the potable water inlet and the grey water to prevent any chance of grey water being sucked back into the mains pipework. In most cases it appears that a normal ball valve as used for cisterns will suffice provided that the water level and overflow are both below the level of the discharge from the ball valve (you will need to check the detail of how much distance is required etc.).

[Pilgrim]

You need to read up some threads from that area, as pretty much every aspect will have been covered over the years.

Have you understood the area lading of the roof  (trusses) & taken appropriate measures?

Have you read water / plumbing regs with regards to  back flow (etc).

Have you seen the thread with the commercial "in roof" diverter as a pre-engineered option on harvesting in a low profile manner, its all there as resources, based on others professional / bodgineered set up.

Your problem is likely grey water / potable inlet (badly put, as I'm no plumber) & potential for contamination via back flow which is why keeping the two separate is / was the route of many. ..since some of those earlier posts there are other options.

You calculated the viable run off as a first step?

Thanks @MRGUS:
- I've had a look through the previous threads, but as I'm not sure what terms I should be searching for, I've struggled to find the relevant previous discussions. Is there a wiki or something where previous information is collated / summarised?
- Yes, the structural engineer has confirmed that the joists (part of a steel frame) will happily take 2 tons of water.
- I've had a look at the water regulations and am aware of the necessity for an air gap or similar to prevent backflow into the mains.
- A filter in the gutter is an option, but access to the roof to clean it will be problematic. I'd rather have the filter in the attic as it would be much easier to access / clean / unblock.
- I calculated the runoff previously and the recommendation was around 1.5 to 2 m3. However, I'm not sure whether I'll have enough space for 2m3, so I thought I would start with a single IBC and consider connecting it to another in the future if there is enough space and I can maintain the temperature of the water below 20ºC.

[Pilgrim]

You don't say anything about the rafters used for the ceiling/floor of the attic, but you need to bear in mind that a full IBC will weigh around 1 tonne - so some reinforcement of the platform you intend to use may be required.

As Mr GUS said if ou want to top the IBC up with potable water you must have an air gap between the potable water inlet and the grey water to prevent any chance of grey water being sucked back into the mains pipework. In most cases it appears that a normal ball valve as used for cisterns will suffice provided that the water level and overflow are both below the level of the discharge from the ball valve (you will need to check the detail of how much distance is required etc.).

Thanks @countrypaul. It seems that it should be fairly simple to set up a ball valve that will top up the tank if it gets really empty. I suppose the more difficult question is the filter. I may get an IBC and see exactly how much space I have to play with once it's in place.

[Moxi]

Hi Pilgrim,

You need to filter before the IBC if at all possible, if you let organic matter in to the IBC it will settle and can start to decompose, leading to odorous water (anaerobic) or algal blooms (aerobic) either of which will cause you significant issue.

Moxi

[Andyr]

If filtering in the loft, the main question is what if the filter blocks up (which it will).... will this lead to any sort of overflow into the property...

[Iain]

Hi
I have rainwater storage of 9000lts. All are fed via filters under gravity and are in the garden/shed. I then feed a header tank with a pump. The header tank then feeds all services under gravity.
So
Could you collect and store water at ground level, then use a pump to keep the header tank in the loft topped up.
I don't think 2000 lts is much storage and you will run out.

I have 9000 lts storage and I think for 2 of us is about right. Has run out once on 10 years.

If you can store at ground level you can add to it easily if needed. You would not need such a big storage tank in the loft.

If you run out of rain water you can use a ball valve with a float arm with a long vertical section. The valve would be 2 inches above the overflow and about 4 inches above the water level. But the float for that valve could be, say 4 inches from the bottom of the tank. Would only cut in when water is at that low level but the valve would be always 4 inches above the water level. If the tank overflowed the valve would still be 2 inches of air gap above the water.
Iain

[peater]

I have a rainwater harvesting system working for almost 10 years. It uses 2 x below ground installed IBC's. It is supplemented by river water.
When there is no rainfall, the stored rainwater will last 5 or 6 days before the river water pump licks in.
There is no growth in the stored water as it is in total darkness. Any light will promote growth.The stored IBC's supply a 50 gallon head tank in the loft, the weight of this (although not a great concern) is supported by the masonry wall and installed with a flood prevention tray (which in 10 years has never been invoked).

It use mains water as a backup in the event of no rainfall and where there is a problem with the rainwater pump (sometimes looses it prime as the input valve sticks over with silt). Problem is I don't currently have a monitor to indicate when this happens, it is so seamless it could be days before I realise  I'm running on mains water 

take a look, it may be of use to you.....

https://www.navitron.org.uk/forum/index.php/topic,4404.0.html

Peater

[Pilgrim]

If filtering in the loft, the main question is what if the filter blocks up (which it will).... will this lead to any sort of overflow into the property...

A good point Andyr. I was thinking about something like a sand filter with an overflow that runs to the external gutter.

[Pilgrim]

take a look, it may be of use to you.....

https://www.navitron.org.uk/forum/index.php/topic,4404.0.html

Peater

Wow! Extremely impressive. I don't think mine is going to be as sophisticated as that!