R O D I Unit Help!

[Aquatic Dreams]

OK ... after looking online I think I see the difference between flow control and the flush kit. My flow control is in the waste line coming from the RO membrane. A flush kit goes before the membrane to flush out any debris correct? However couldn't I easily just disconnect the tubing from the RO membrane and let it flush out that way?

BTW - This unit won't be in constant use. I'll just be using it once every couple weeks to make RO/DI water that I put into 5 gal. jugs and other containers.

 

[Pipes]

Not everyone flushes the membrane. In residential use it's a rarity. The flush valves I have seen are basically as follows.

Tee before DLFC, to valve, to tee after DLFC. Its really just a drain line flow control bypass valve. It allows excess water to run through the center of the membrane (to drain), supposedly to rinse off the top of the membrane.

I would think that everyone has a post RO tee and valve to run down the TDS prior to running the Ro water through the DI system, provided they use DI that is. All ROs run a high TDS when first started, then as pressure builds in the membrane, TDS drops.

 

[Aquatic Dreams]

OK ... so I've got the unit almost up and running. I flushed the Sediment filter for about 5 mins and then the Carbon filter for 5-10 mins. Just hooked up the new RO membrane. I did a quick full flush on it for a minute or so and then inserted the flow restrictor back in the waste line. I checked the TDS just to see the difference. The waste line is at 174 (higher than my tap water) and the RO output is 12. How long should I let this run before hooking up the DI canister? And the pressure gauge is reading about 72 psi with the tap open full. Is this acceptable or should I turn it down a bit?

Also I watched a few vids on adding the DI resin to the cartridge. Many of them showed a foam piece to put on top of the resin before putting the cap on. Mine doesn't have this extra foam piece. So do I just fill it to the top making sure it's nice and tight along the way and then put the cap on?

 

[Pipes]

NSF, drinking water standards, state anything under 20 PPM is acceptable. But with running to a DI you want it as low as possible. Keep checking to see if the PPM drops as it runs. You don't have to flush the membrane every time you run the RO. TDS always starts high, then as pressure builds in the membrane, the TDS drops. You may be lucky and have it drop below the 12 as it runs.

The foam disk that goes in the bottom of the canister is to keep the resin from tumbling. Once the resin is in place, the foam disk compresses to account for any packing that may occur once the water is running through the media.

 

[Aquatic Dreams]

NSF, drinking water standards, state anything under 20 PPM is acceptable. But with running to a DI you want it as low as possible. Keep checking to see if the PPM drops as it runs. You don't have to flush the membrane every time you run the RO. TDS always starts high, then as pressure builds in the membrane, the TDS drops. You may be lucky and have it drop below the 12 as it runs.

The foam disk that goes in the bottom of the canister is to keep the resin from tumbling. Once the resin is in place, the foam disk compresses to account for any packing that may occur once the water is running through the media.

Well I figured 12 was good since I checked just after I added the RO membrane. I expect it to drop closer to zero after I add the DI portion. How long do I let it run though? I've read some places that say an hour or so which seems excessive to me.

As for the DI cartridge I don't need a foam piece for the top then? (Where the cap screws in.) There is a foam piece at the opposite end of the cap however some of the vids I watched had a foam piece at both ends. I'm just trying to find out if this is necessary.

 

[Pipes]

Some times the TDS drops after 10 min, some times that's all you get. Depends on the membrane. Running for an hour is a waste, considering the waste to product ratio of 3:1 or 4:1. That means 4 gallons down the drain to every gallon of product.

The refillable cartridges I have open on the bottom and have no foam on top. There is a screen in the top to keep the product/resin in. Product goes in until almost full, tap on counter top, insert foam, screw bottom on, insert in canister and flush/run. Make sure you have it right side up. The rubber washer is at the top. Most canisters are tapered with the top being narrower. Bottom usually has slots cut in the flat surface. The foam is just there to keep the resin from tumbling. Holds it in place. If the resin tumbles, it will cause it to fail prematurely. Think of it as pebbles tumbling in water. After a few million collisions you have beach sand...

 

[Aquatic Dreams]

Just checked again and the RO is at 9 and the waste is at 180. The cartridge that I have has foam wedged into the top. (The end with the rubber seal) There is NOT another piece of foam for where the cap screws on. I can take a pic if you like. Will this be an issue?

 

[Aquatic Dreams]

Actually I just did a search online. This is the one I have. Guess it doesn't need to have foam at the bottom. I'm going to have to fill it really full then I imagine.

 

[Dan Cole]

Your TDS (9) is a bit high. Your membrane should have a rejection rate of about 98% so with a initial TDS of about 180 you should have a TDS around 3.6. You'll go through DI carts a little quicker so keep an eye on both the TDS coming out of the membrane and DI. If your DI is above zero get ready to replace it...it will go down hill in a hurry.

Dan

 

[Pipes]

Hmm. Guess yours doesn't have a foam. Mine is similar, but with the foam on bottom. Must be a different manufacturer. After you fill it with the resin, give it a gentle tap on the counter top to seat the resin. You might find you can get a little more in.

As a side note (of humor). I went to a service call a couple of years ago, to look at an RO that was leaking. The home owner filled his cartridge with carbon and put it in upside down. Apparently Home depot said "You can do it we can help". The other half of the motto is...."but maybe some people shouldn't". Guess that's what you get for drinking Ingersoll water...

 

[Aquatic Dreams]

Your TDS (9) is a bit high. Your membrane should have a rejection rate of about 98% so with a initial TDS of about 180 you should have a TDS around 3.6. You'll go through DI carts a little quicker so keep an eye on both the TDS coming out of the membrane and DI. If your DI is above zero get ready to replace it...it will go down hill in a hurry.

Dan

OK ... just to be clear my tap water is coming out at about 132. I just checked again and the waste water from the RO unit is at 183 and the RO water is still at 9. I had heard to expect it to be below 20ppm so I figured that 9 was pretty good no? It's been running for about half an hour or so now.

 

[Pipes]

That's not bad. I'm assuming you don't have a water softener in London, which is 7 hard. I'm close to 25 hardness, so I have a softener ahead of my RO, which is running around 9 PPM. Mine starts off at 40 PPM and within 10 mins it's down to 7-9 PPM depending on the day.

 

[Dan Cole]

If the tap water is around 130 then your TDS after the membrane should be closer to 3. I don't know the history on your RODI but did you change the membrane recently or something? Do you know if the flow restricter matches the rated GPD for the membrane? To me your output TDS after the membrane is about 3 times higher then it should be for some reason.

 

[Aquatic Dreams]

Hmm. Guess yours doesn't have a foam. Mine is similar, but with the foam on bottom. Must be a different manufacturer. After you fill it with the resin, give it a gentle tap on the counter top to seat the resin. You might find you can get a little more in.

Yeah ... I'll just be sure to pack it nice and tight!

As a side note (of humor). I went to a service call a couple of years ago, to look at an RO that was leaking. The home owner filled his cartridge with carbon and put it in upside down. Apparently Home depot said "You can do it we can help". The other half of the motto is...."but maybe some people shouldn't". Guess that's what you get for drinking Ingersoll water...

HA ... good one. Actually I was talking with the Home Hardware guy today. He was interested to learn more about this RO water setup. I ended up getting a 2-pack of RainFresh Head O-Ring Seals that seemed to be the size I needed for the canister. They certainly didn't seem to know much about RO units even though they sell a couple parts. LOL Apparently the water they've been selling me is just filtered water. I checked the TDS after flushing the Sediment and Carbon filters and it was identical to the 5 gal. jugs I was filling there.

So is it safe to install the DI section now? Or should I run the unit a bit longer to see if it drops more? And how long should I flush the DI canister for?

 

[Aquatic Dreams]

If the tap water is around 130 then your TDS after the membrane should be closer to 3. I don't know the history on your RODI but did you change the membrane recently or something? Do you know if the flow restricter matches the rated GPD for the membrane? To me your output TDS after the membrane is about 3 times higher then it should be for some reason.

This is a previously used RO unit that I just purchased all new filters for. Today I replaced most of the tubing and one o-ring for the DI canister. I wasn't aware that the membrane had to be matched to the flow restrictor. I got the only membrane that I could at the time and it's rated for 100 gpd. I was just going to get the 80 gpd one but they didn't have any in stock. Could I just reduce the flow a bit to compensate?

BTW - I just set everything up an hour or so ago if that makes a difference.

 

[Aquatic Dreams]

Actually I just read about the membrane that I purchased. It states that a new membrane should have a minimum of 90% rejection rate.

 

[Dan Cole]

So you have a flow restrictor rated for an 80 gpd membrane but are using a 100 gpd membrane? Is the flow restrictoor a valve, pig tail or some other type? If it is a valve type you can adjust it, you might also be able to tweak the pig tail type but otherwise you should hunt down a flow restrictor to match that membrane. As it stands you're not creating the correct amount of pressure to push water through the membrane properly.

 

[Dan Cole]

Actually I just read about the membrane that I purchased. It states that a new membrane should have a minimum of 90% rejection rate.

I would get a new membrane otherwise you'll be going through 3 or 4 DI's for every one that you should be going though.

Dan

 

[Aquatic Dreams]

I don't know that the flow restrictor is rated for 80 gpd. I was just initially going to get that membrane as I don't need to make a lot of water and it was a bit cheaper. However I ended up getting the only membrane they had. I wasn't aware the the flow restriction had to be matched to the membrane. I hadn't seen any of the many many threads I've read or any videos suggest that.

The unit I have is a SpectraPure MBDI 90. Perhaps the 90 means that it's meant for 90 gpd? The flow restrictor is a little tube like piece that sits inside the waste tube. There are pics of the unit and the flow restrictor earlier in the thread. Here is a pic of the flow restrictor again ...



I can get the pressure up to around 72 psi and can obviously drop it from there if necessary. I don't think I'll be getting another membrane unless I can find somebody that wants to trade for their new lower gpd membrane. So I'll likely have to find a way to make do with what I have.

 

[Dan Cole]

That's a SpectraPure pig tail style but your problem is the crappy membrane...you can use it, just be prepared to spend any money you saved on replacement DI cartridges or refills - plus some. When you buy a membrane be sure to get the highest rejection rate that you can...think of it this way...if you have a membrane with a 98% rejection rate and you go through a DI every 3 months...the DI cartridge would last 6 months if your membrane had a 99% rejection rate. The TDS going through a membrane with a 99% rejection rate will be half that of a membrane rated at 98%.

Dan