31 replies to this topic

[MikeP]

No thats where it was connected when it arrived.

[osmosis]

MikeP, on 26 May 2011 - 16:31 PM, said:

Typically its now pissing down in South London.....

Yes, I connected up my emergency unit - £100 of membranes and cartridges - and then it chucked it down all day

Now got to find out how to store a membrane without it rotting

Dave

[mobile]

I've never had any problems with RO membranes rotting but I know that some aquarists store them wet in the fridge, i.e. in a sealed bag containing some RO water (maybe wrapped in clingfilm prior to putting them in the sealed bag?).

[Flytyer]

I am seriously thinking about buying an RO unit in the near future but have a couple of questions....

Do you have to plumb them into the mains water or can you use a hosepipe or some other means of water supply?

I've read somewhere (on this forum?) that they produce a lot of waste water, approximately how much waste water per litre of RO water?

I was thinking of using it as a standby in case I run out of rainwater, but if it can produce all the water I need, that's two waterbarrels I can use for other plants.

Thanks for any replies, and sorry if the questions seem daft  

[mobile]

Flytyer, on 07 June 2011 - 19:10 PM, said:

Do you have to plumb them into the mains water or can you use a hosepipe or some other means of water supply?

You can get adaptors for connecting them to hose bib taps.

Flytyer, on 07 June 2011 - 19:10 PM, said:

I've read somewhere (on this forum?) that they produce a lot of waste water, approximately how much waste water per litre of RO water?

This is true, they waste a lot of water. Typically, if it is uses a flow restrictor,  there is between a 3:1 and  6:1 reject rate, with 4:1 being quite common, i.e. for every 1 part pure water produced, 4 parts are rejected. The reject rate is also dependant on pressure and temperature, with higher values of both being more efficient, but you're unlikely to get below 3:1 without using booster pumps and secondary membranes. Dependant on the quality of the feed water, pressure, temperature and required product water, the reject ratio could be 10:1. The reject water can be used for purposes that do not require pure water, bearing in mind that it will contain the contaminates that the RO membrane has rejected.

[Flytyer]

Thanks for the info Mobile, I'll make sure to buy the proper connectors when I buy it. I'm surprised at how much rejected water there is though, no doubt I'll find some way of using it up  

[MikeP]

I had to go and buy the final connector to join mine to the end of a hose pipe. RO-Man supplied a fitting with a female thread which would have fitted onto a Bib tap but if you want to connect to the far end of a garden hose you need to get the corresponding male threaded Hozelock Threaded Accessory Adapter ( 3/4 inch Ref number 2289) to join it all together.
I bought an extra 6m of pipe so that I could use the 'waste' water to water parts of the garden near the greenhouses. Before the recent welcome rain I had made two butts full of RO water and usefully rescued a very parched section of shrubbery so i felt that the excess water had gone to good use.

[mobile]

MikeP, on 07 June 2011 - 21:19 PM, said:

I had to go and buy the final connector to join mine to the end of a hose pipe. RO-Man supplied a fitting with a female thread which would have fitted onto a Bib tap but if you want to connect to the far end of a garden hose you need to get the corresponding male threaded Hozelock Threaded Accessory Adapter ( 3/4 inch Ref number 2289) to join it all together.

I don't know how much the RO-Man/Hozelock combination costs, but you can purchase a suitable assembly on eBay, it's called a 'CONNECT 1/4" REVERSE OSMOSIS PIPE TO HOSE PIPE'

[MikeP]

The female threaded part came with the unit but I paid £2.99 for the Hozelock male connector. Having had the unit delivered and in dire need of the RO water I went to my local garden centre and paid the asking price..........now of course SE23 is inundated with rain.......ho hum.

[David Ahrens]

One of the problems with RO, possibly the main problem with RO, is the large amount of waste water. At work, we pick up parcels from a shop  that grow live corals for fishtanks. They use RO and I got talking to them one day. They have got the waste water down to one to one, pure water and waste. They do something like backflush the membrane. I am not exactly sure what they do but I could find out if people are interested. Apparently, this does shorten the life of the membrane very slightly, maybe by 5% or 10%.
If anyone is interested what they do to reduce their waste water, I can find out. Do give me a little while as I haven't picked from these people for a while, but I could pop in and ask them.

[mobile]

David Ahrens, on 15 June 2011 - 18:59 PM, said:

One of the problems with RO, possibly the main problem with RO, is the large amount of waste water. At work, we pick up parcels from a shop  that grow live corals for fishtanks. They use RO and I got talking to them one day. They have got the waste water down to one to one, pure water and waste. They do something like backflush the membrane. I am not exactly sure what they do but I could find out if people are interested. Apparently, this does shorten the life of the membrane very slightly, maybe by 5% or 10%.
If anyone is interested what they do to reduce their waste water, I can find out. Do give me a little while as I haven't picked from these people for a while, but I could pop in and ask them.

Backflushing the membrane is a method of cleaning the membrane of mineral deposits. Some RO units come with something called a flushing valve, which simply bypasses the flow restrictor, therefore increasing the water flow across the membrane surface and supposedly loosening and flushing the deposits, though this is not truly backflushing. This valve is manually operated periodically. It will not decrease the amount of waste water by any significant amount though. One common method of reducing waste water is to fit a second RO housing and membrane, the waste from the first membrane is then fed into the second. This requires the flow restrictor to be moved to a point after the second membrane. Another method is to collect and recirculate the waste water through the RO unit. This can be done by collecting the waste water in a storage container and using a pump to re-pressurise it, passing it back through the RO unit. With this method it is necessary to monitor the waste water TDS, as the ever increasing levels of minerals will eventually clog the RO membrane. I suspect that the coral growers use one of the aforementioned methods and also backflush the membrane to help remove some of the additional minerals that result from using them. I would be interested in knowing which method they use, if you get chance to ask them.

[David Ahrens]

Give me a little while on this, it may be a while before I go there again.