Ro Water Tds

[cooper1973]

i have just bought a tds meter to test my water and its reads 020ppm is this to high to consider safe to use? my tap water is 360 ish. my ro water was 061 but the longer i kept it running it was coming down. i left it running alnight and now down to 020ppm could this indicate a well used membrane

 

[cooper1973]

and is it correct that anything under 050ppm is ok to use?

 

[seffieuk]

i have just bought a tds meter to test my water and its reads 020ppm is this to high to consider safe to use? my tap water is 360 ish. my ro water was 061 but the longer i kept it running it was coming down. i left it running alnight and now down to 020ppm could this indicate a well used membrane

It is ok to use but you would obviously be better off using water that has a TDS of 0. Running the water over night probably helped flush the membrane, are you keeping it wet between water changes? and have you got a DI filter on it, if not, buy one, it would probably bring the reading nearer to the 0 and they are not that expensive, around £10 ish

Seffie x

 

[cooper1973]

i have just bought a tds meter to test my water and its reads 020ppm is this to high to consider safe to use? my tap water is 360 ish. my ro water was 061 but the longer i kept it running it was coming down. i left it running alnight and now down to 020ppm could this indicate a well used membrane

It is ok to use but you would obviously be better off using water that has a TDS of 0. Running the water over night probably helped flush the membrane, are you keeping it wet between water changes? and have you got a DI filter on it, if not, buy one, it would probably bring the reading nearer to the 0 and they are not that expensive, around £10 ish

Seffie x

it has the sediment filter and carbon filter + membrane ad a post carbon filter. the ro unit has a permenant water supply i never switch of there is a constant waste flow coming out

 

[seffieuk]

it has the sediment filter and carbon filter + membrane ad a post carbon filter. the ro unit has a permenant water supply i never switch of there is a constant waste flow coming out

Gosh that is a lot of wasted water. To save water fit two ball valves to the pipes, that way you can keep water in the pipes but not be wasting water. I really would recommend a DI unit, it will probably bring down that TDs reading to 0 and they are easy to fit to the existing unit

Seffie x

 

[cooper1973]

can i remove the post carbon filter and add a di filter

 

[AK77]

can i remove the post carbon filter and add a di filter

You can get a DI filter and hook it up between the membrane and post carbon filter. I wouldn't bother removing the post carbon filter.

Here is a picture of what my unit looks like. I've since removed the valve from the yellow pipe (waste) as some idiot shut it one time!

As you can see, mine is a 6 stage. 3 prefilters, membrane, DI unit and post carbon filter. My TDS is still reading 0, even though I haven't changed the filters in well over a year. I probably won't do until the meter starts registering something.

 

[rabbut]

Sorry, I can't help but but-in with this much wrong info in an RO unit thread

You cannot fix your current issues with DI alone. It should be clear to anyone that knows anything about RO units that the membrane is knackered. A correctly functioning membrane will produce product water with a TDS 1/100th of the feed water. That means that on your supply, a correctly functioning membrane will be producing water with a TDS of 3.6ppm - most meters will round that up to 4ppm. To get a reading of 20 from the membrane, 5 times higher than it should be, clearly shows the membrane has gone

Question is why. Well again, for anyone who knows what they are doing with an RO unit, the answer should be obvious. You are running the unit all the time, regardless of how much water is going though the unit. Carbon pre-filters (usually the second filtration stage) have a finite life, according to how much water has passed though them. Typically this is 2,500 gallons, but can be as much a 5,000 or as little as 1,000. This is the total water passing though this filter, not the quantity of water you are producing. As both waste and use water passes though this filter, while the unit runs while not producing water, the life of this filter is ticking down. If the unit runs for more than a fortnight just ditching water to waste (that would knacker your membrane eventually anyway) this filter will run out of life and allow chlorine/chloramine in your tap water to get to your membrane. These two chemicals will kill a membrane if they get into contact with it, hence why you have a carbon pre-filter - to remove these chemicals and protect the membrane from damage.

Also, if water is constantly going though the unit, I'd imagine your sediment pre-filter is far from in good nick and probably near spent also.

You need to replace the Carbon pre-filter and membrane for definite. I'd recommend replacing the sediment pre-filter also, unless there is a notable pressure drop between the feed into the membrane and into the unit, then it definitely needs replacing. It's likely the post-carbon filter also wants to be replaced, but this is just a way for manufacturers to get more money out of you for a filter you don't need IMO. It's probably past it's rated useful life, but as it does very little, you can ignore/remove it if you wish.

As you are running water though the unit constantly however, you are going to currently be needing to replace pretty much all the filters on a rolling fortnightly basis. For this reason, I'd suggest you need to add a valve to turn the unit off. If you turn a unit off, you should really also close off the use and waste pipes also, to avoid the membrane cartridge draining the the membrane drying out. If the membrane drys, it's knackered.

So, essential replacements are;

The carbon filter
The Membrane (assuming a 50gpd unit here)
Flow Restrictor (note you should always replace the flow restrictor whenever you replace the membrane. Also note I'm assuming a 50gpd unit here)

And recommended replacements are;

The sediment pre-filter

Recommended new bolt-ones;

Three ball Valves (assuming you have none already. You want one of the feed, use and waste to preserve the life of your filters)

All the best
Rabbut

 

[cooper1973]

looks like im getting different opinions now this is interesting the last post would seem more apropriate as it has been explaind to me alot more what goes on. now i know its more expensive but looks like i will be replacing membrane and filters as i dont know what the bloke had done with this b4 i bought the unit ie has he ever replaced filters etc. i have had the membrane out and run under the tap but you cant tell if this is faulty other than tds reading so think i will change all filters and see what happens

 

[rabbut]

You'd be best off getting some valves for it too, that way you can turn it off completely when not in use and keep the filters "fresher" for longer

 

[cooper1973]

yep i already have the valves which i have fitted one on each pipe so now when im not using it i can shut them all off and keep water in there i was told not to put one on the waste pipe as it has organics flow restrictor but the water just constantly flows from the waste when im not using the systen surly that was not good so i have fitted the valve so when im going to use the system i will run the waste one for 20mins or so b4 taking water just so it flushes through. i am going to replace all filters as i dont know the age of the......thanks for your advise

 

[seffieuk]

Of course Rabbut is the guru as far as RO units go BUT I had assumed obviously wrongly that you had not been running the RO unit 24/7 for very long? If this is the case, I really would have tried the DI unit first - I had the same sort of readings, bought all new bits and bobs including a new membrane, added the di unit first, luckily, tested the water and it came back with 0!

Rabbuts suggestion of the ball valves echos my own suggestion!

You mention in your last post that the unit is second-hand, so now I have all the facts I agree totally with Rabbut about replacing everything plus buying a DI unit and ball valves.

So to clarify, no difference of opinion just that Rabbut and i made different assumtions - and yes, before anyone says it ' never assume anything!'

Rabbut, I'm tired and cranky so probably misreading your first comment, or perhapes taking it the wrong way - you are indeed the King of the Ro unit and are entittled to put us right, but there is maybe a friendlier way of doing it - maybe you are also tired and cranky!

Seffie x

 

[cooper1973]

hey peeps lets not get into any arguements over this..............your all such a great help all infomation is very appreiated as i have done tropical for about 3>>4yrs and only just started the marine side of things so all infomation is great i will try a di unit aswell as changing filters etc. i have now fitted the ball valves to my pipes so when not in use i can turn them all off keeping water inside my ro unit. as i say i am new to all this and i thought the waste pipe had to be running all the time as the guy i bought the unit from had no ball valve fitted to the waste pipe which gave me the impression it would constantly flow but i can see now this is not the case.......your helps great thank you

 

[rabbut]

Sorry seffie, posted that in rather a hurry and didn't proof read it. Reading it back it does not come across as friendlily as I'd have liked Apologies if it's caused offence

you could use DI on that to drop the TDS further, but you are pumping water out at a really high TDS into the DI, so it ain't gonna last long. A well maintained membrane will last years (5+), and with a Di attached, the DI should last a good 12-18 months under "normal" use With that higher TDS going to the DI though, I 'd expect the DI to last a few weeks at most, and DI is expensive to keep replacing, particularly if your using it due to a bust membrane. Long-term replacing the membrane if it's pumping out water with a high TDS will always be the most cost-effective option out of replacing the membrane or using DI

I'd apply ball valves to the feed, waste and use pipes. When you turn off, it's use then waste then feed valves that turn in that order. When turning on again you do feed, waste use in that order You should have a flush valve on the waste pipe, allowing your flow restrictor to be by-passed. Open that for 1/2 an hour before and after running off your RO, and ditch the first 1/2 hours use water after closing the flush valve. Also, you want to by-pass the DI if you are using it, as the flushing and the first 1/2 hours use water after a flush will have a high TDS and will "waste" the DI as the water goes though it...

Personally, I advocate not using DI. It's counter productive... When you get down to single digit figures on your TDS it's all Organic Carbon that you have left. The ULNS guys add Organic Carbon, via Vodka, Sugar or Vinegar, as food for bacteria. If you remove this "food", you are more likely to get Algae though Phosphate and Nitrate build-up. Adding the OC in your top-up/water-change would otherwise be feeding your good bacteria, something that won't happen if you polish the perfectly good TDS of 4ppm down to 0ppm with DI

 

[cooper1973]

mmm very intresting plenty of info for me to go on. i can see that the membrane is damaged as there is no flush valve on the unit so looks like this has not been proply flush. it has the flow restrictor which i am going to replace but there is no flush valve which i think i will fit one