RO/DI - TDS - Evaporation Top Up

[ander88]

Good morning.

I have a few questions relating to RO/DI, TDS etc.

Since I started my tank back in April Ive been mixing my own salt water using a RO/DI filter. Ive also been using the RO water for top-up due to loss in evaporation. Up until now I have not had a TDS meter.

Now I have a TDS meter I've measured my tap water to be 172ppm and the water coming out of my filter at 110ppm.

My LFS will only sell me pre-mixed saltwater and no RO/DI water for some reason.

What my main question is, is my filter running wrong with such a high output( if 110ppm is high) and should I get a better filter?

Also, I have read on various forums etc that I should be getting a tds of 0ppm from my filter and anything below 90% efficiency I should change filters, is this correct?

Water Top - Ups
I Have also read that I should not be using pure RO/DI water for my top ups as this will lead to my fish dieing? Is this correct and what should I be using for top-ups.

Basically Im back to square one with all my water chemistry. I thought I was doing the right hting but seems im not......

Thanks in advance, Michael

[Sploke]

It is correct that you should be getting 0 or near-0 TDS from your RO/DI system, especially since your source water TDS is not all that high. I would replace all the sediment and carbon filters, the RO membrane and probably the DI resin as well.

As for top-ups, I use RO water for topping off my reef tank, but I also dose with a 2-part supplement to maintain alk and Ca. Others use RO water with kalkwasser in it for the same purpose.

[ander88]

OK, so I'm not doing anything wrong topping up with RO water but I should be adding some supplements to keep the levels up? What supplement do you use?

[fsn77]

Sorry to hear you're having problems with your RO/DI unit. Luckily, it shouldn't be too difficult to solve these problems.

The water coming out of your RO/DI unit really should have a TDS of 0, otherwise something is not working quite as it should.

Is your tap water from a well or municipal drinking water system?

Has your RO/DI unit been connected only to a cold water supply line? Water that is too warm will destroy the RO membrane.

I would take your RO/DI unit apart and see if there's actually a RO membrane in the membrane housing. I've read accounts where people bought a RO/DI unit and the manufacturer did not install the RO membrane. Unfortunately, they don't find this out until after hooking it up and having some ability to measure the unit's performance (unless they watch the waste to product water ratio, which would be off). This doesn't happen all that often (I've only read of this happening a handful of times), but it's certainly easy enough to check.

If there is a RO membrane in the membrane housing, be sure it is seated fully in the housing. If not, the membrane will not work right and water can seep around the membrane.

If the RO membrane seems like it is properly installed (it will be very snug in the housing), check all the tubing / lines to make sure they are going to the right places. Also, check to be sure there's a flow restrictor on the waste water line coming out of the membrane housing. It can be a capillary style restrictor that is inside the end of the waste line tubing at the connection to the membrane, or it can be a cylinder about the size of your pinky finger that's installed inline on the waste water line. Without a little knowledge of how RO/DI units function, all of this might not be the easiest thing to do on your own. Feel free to post a decent drawing and/or close-up pix of your RO/DI unit if you need help.

Do you know what your waste to good water ratio is? Idealy, it should be about 4 gallons of waste for every 1 gallon of good water, but it's not uncommon to see 5:1 or 6:1 if the water temperature, pressure, and/or TDS are not so good.

A properly functioning RO membrane lasts anywhere from 3 - 5 years, and yours should be on the longer side of that considering how low your tap water TDS is. The pre-filter cartridges should be replaced about every 6 months (unless they have clogged earlier). The DI resin should last longer than the pre-filters. Is your DI resin the color changing variety? If so, then it must be completely orange/brown by now with 100+ TDS coming out of your unit. While relying on the color change itself is not 100% recommended, it at least provides a rough idea when you need to start paying more attention and be getting ready to change it out.

Supplements should only be added to your tank if you need to add them. Decent test kits for calcium and alkalinity will show you if you need to dose those. That said, when topping off your tank, it is very much a perfect time to dose if dosing is needed. However, it is not recommended to dose calcium and alkalinity at the same time, as it can a reaction between the two that results in the a white percipitate clouding up your tank.

[ander88]

Hi fsn,

Ill start from the top of your post and work my way through,

Water is from a municipal system
RO Unit is connected into the cold water system
RO Membrane seems to be in the housing and fitting properly

Ive checked the tubing and it all seems in the right place. I never altered any when taken out of the box either.

What im stuck with now is the waste line. Here is a picture of the waste line. Unsure if this is correct or not. It has a stopper in the end. (orange piece)

Waste water ratio I have no idea, I think the waste line may be wrong.....

THe resin part is orange brown, it was orange to start with. It has went from being free moving to cloggy.

Here are various pictures of my unit. Blue pipe is the inlet pipe from the cold water system which I only turn on and off with a tap. The white tube is the outle which goes into a large bottle. I have no restriction on this.

I think I need to get a better unit as by looks of it I can only change the RO/DI filter, the rest are all sealed, unless this is normal too?

Having Issues with card reader on laptop for pics. Get pics up ASAP

[ander88]

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14312
RO Membrane Chamber

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14313
Post Carbon Filter

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14314
Dirt and Sand Reduction

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14315
DI Unit

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14316
Drain Valve

http://www.aquariacentral.com/forums/picture.php?albumid=1531&pictureid=14317
Complete Unit

Tap Water In > Post Carbon > Dirt and Sand Reduction > RO Chamber > DI Unit > Water Out

[Amphiprion]

One recommendation is to get rid of those horizontal DI canisters and switch them for the vertical flow-through type. Not sure where you can find inexpensive parts in the UK. That should improve the TDS reduction and the usable life of the DI resin, as well.

Another question: what is the TDS directly out of the membrane (before DI)? Also, is that flow restrictor in pic 5 actually connected?

[ander88]

Unsure of TDS reading before DI. Will disconnect and have a go at taking that.

You mean on the drain outlet? One end is connected to the membrane chamber and the other to that orange plug thing. Ive never done anything with it? didnt no i had too?

[Amphiprion]

Just making sure the waste/drain line is connected to the flow restrictor (thing that says "drain," "800," and "flow -->").

[fsn77]

First off, your RO/DI unit is a little different than the typical unit here in the US. But, the principles in which they work are the same. It would appear that your pre-filters are ones that you replace the housing and all (not just open it up and replace a cartridge).

Whoa... If there's no line coming out of the flow restrictor, are you saying that you do not have a waste water line? If so, all of the water you're putting into the unit is being forced through the RO membrane, which is why you are seeing the kind of TDS levels that you are. This has likely ruined the RO membrane.

While it appears there's a good amount to correct, hopefully doing so will save you from any unnecessary headaches with your tank.

If you want a better RO/DI unit, it very much seems like this would be a good time to buy one. I'm not sure what your options are in your country, but I'm sure there's plenty of us that'll share our opinions if you want to post pix and/or links to ones that are available.

[Amphiprion]

Another observation is that the sediment and carbon are switched. I would be willing to bet that even if you bought all new filters, they wouldn't last long at all in that configuration. Do you know to what size the particles are filtered to in the sediment and carbon stages? I didn't notice at first that you were in the UK, so my previous source for filters doesn't really apply.

[ander88]

Just making sure the waste/drain line is connected to the flow restrictor (thing that says "drain," "800," and "flow -->").

Well it is connected to the housing, but then the flow restrictor goes nowhere. Its blocked off. No drain line or anything.

[ander88]

No Amph Im sorry I dont know the particle sizes.

I think I need to buy a new unit with a proper instruction manual and start from scratch. Time for a new thread I think when I get some reading up done on the better types of filters.

So your saying that Horizontal versions are better than vertical?

[Amphiprion]

Other way around. Vertical > horizontal, since water has to be forced through it against gravity.

[ander88]

OK vertical it is. Having a look around now.

[kj5kb]

I've been researching these heavily as I am moving to SW and also wanting to improve my drinking water. There are loads of places on the www that explain how RO works, here's one:

http://www.home-water-purifiers-and-filters.com/reverse-osmosis-filter.php

Basically tho, you MUST have a drain line conected to the waste valve. RO wastes much more water than it makes.

Just Curious...Is your water metered or do you pay flat water rates no matter how much you use?

Typical order for a 4-stage unit is:
Sediment>Carbon>RO>DI

However with that type of carbon filter the intent may have been to use the sediment filter to keep the carbon fines out of the RO unit (???)

Eventually, you might want to upgrade to something with replaceable cartridges...replacing those sealed filters may get a bit pricey.
Something like this from H20Splash on ebay:
http://cgi.ebay.com/Reverse-Osmosis-System-75-Drinking-Water-Aquarium_W0QQitemZ400029397137QQcmdZViewItemQQptZS mall_Kitchen_Appliances_US?hash=item5d239c3091

For now, I'd add a drain line and use what you have...see how it works.