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RO/DI system upgrade

gcodrutv

Member
Joined
2 May 2019
Messages
51
Location
Dublin, Ireland
Hi all,

I know this subject has been discussed on numerous times, but I would like to hear your opinions.
My current setup is a 350l long planted tank and I'm doing a 80-100l/week water change.

The tank is fed by a 4 stage mains filtration system composed of 1 micron sediment filter , followed by 2nd and 3rd stage of 1 micron Pentek Chlorplus and the 4th stage is a 0.5micron Pentek carbon block.
Incoming TDS on the mains water (before filters) is varies from 70 to 90ppm.
Because my Silica levels on the tap water are measured to about 6ppm and ongoing battle with Diatoms, I was thinking to add a RO/DI to the existing filtration system.

Ideally I was looking to get 2 300gpd RO membranes in series with a 600gpd pump, followed by a DI stage .
This way I can do a water change in about 2 hours. (ideally). Don' have the necessary space for the water storage.

Any recommendations for suppliers / membrane brands ?

I was looking at:

https://vyair.com/product/300gpd-32lph-3012-reverse-osmosis-membrane-element/ --- Turkish brand/made
https://www.osmotics.co.uk/300-gpd-reverse-osmosis-membrane.html --- Chinese brand/made
https://www.finest-filters.co.uk/vontron-300gpd-ro-membrane/ --- Chinese brand/made
https://www.devotedly-discus.co.uk/acatalog/Axeon-500-US-GPD-membrane-6_0012.html#SID=32 --- Unknown made
 
my Silica levels on the tap water are measured to about 6ppm and ongoing battle with Diatoms
I often dose dissolved silica in my tanks. I've never observed it to cause diatoms.
In this forum, we have discussed diatoms several times. There's an opinion that diatoms are poor competitors against other algae, and perhaps microbes as a whole.
One more note: They say that RO is not particularly effective against silica/silicates.
 
Forgot to mention,

Option no.2 would be 4 membranes, 2 sets of 2 in series and the output in parallel.
Price wise is almost the same. A good 150gpd membrane is about 45£ and a Chinese/Turkish 300gpd is about 75-80£.

It will be an initial extra costs for 2 RO housings.
 
They say that RO is not particularly effective against silica/silicates.
You are absolutely correct on this. RO is rejecting only 50-65% of silica, this the reason why a DI stage is necessary.
DI resin will remove the remaining 45-50% of silica, but has to have almost pure water for ion exchange to take place, otherwise the resin will interact with other chemical compounds form water and will be exhausted very quickly.
If my calculations are correct, a 300ml DI cartridge will be consumed in about 100 to 150l of water with TDS under 100ppm.

I'm not a big fun of RO/DI, but from what I read, silica is the root cause of diatoms.
To eliminate this, RO seems to be the solution.

In the past I had for about 5 years a 120l tanks and never had diatoms. I was using only RO/DI from the local shop.
No, I got lazy and I don't want to get 4-5 barrels f RO every week, very time consuming. My water changes are automated, the entire tank is controlled by a computer.
 
Hi all,
I'm not a big fan of RO/DI, but from what I read, silica is the root cause of diatoms.
I often dose dissolved silica in my tanks. I've never observed it to cause diatoms.
I'm <"not convinced"> either, but could you use rain water? Difficult I suppose with a big tank and an automated system.

cheers Darrel
 
Hi Darrel,

I can't use rain water, don't have any space for water storage.

Thank you
Gabriel
 
Hi Gabriel,
Just an FYI - Finerfilters also sell the Vontron membranes (300gpd is out of stock currently) which are generally much cheaper than the alternatives you listed above.

They also sell "membrane upgrade kits" which should give you the membrane housing, membrane, and most of the fittings you need to add RO membranes to your system.
 
Hi Gabriel,
Just an FYI - Finerfilters also sell the Vontron membranes (300gpd is out of stock currently) which are generally much cheaper than the alternatives you listed above.

They also sell "membrane upgrade kits" which should give you the membrane housing, membrane, and most of the fittings you need to add RO membranes to your system.
Prices are very good.
How long will last the Vontron membranes ? I could not find anything online or any users that have tried them ?
I read loads of reviews of membranes failing in 1- months of use.

One thing if you know, how loud would be a booster pump ?
My main water pressure is very low and will need a pump.

Thnak you
Gabriel
 
I can confirm that the prices are attractive even for me - living in a cheaper country.
UK was my main shopping destination before Brexit, now...
 
Cannot comment on the Silica and Diatoms, though think you ought to follow up on the link from @dw1305 his advice on such chemical matters is very good.

You say you never had any problem when using your LFS RO water, but do you know exactly what their RO system is made up of ? would like to bet it uses standard filters and membranes, have you asked them ?
Before spending more mountains of money on excessive equipment, why not fit a standard 4 stage 150 GPD and see if that reduces the silica and diatoms ?
It should take about 3 hours to produce 90 lts.
You can also buy a cheap tap water pressure gauge to see what pressure you really have.

If Silicates etc is your problem, though you can change all the water, wonder if over time they can settle into the substrate ?
 
My LFS has a commercial RO system with an huge pump. They use 20" filters and much larger memebranes.
They are specialized in reef tanks and tropical as well.

They recomended D-D Aquarium membranes. (Ofcourse, because they sell this).

My mains pressure varies from 0.9 to 1.1bar (13 - 16 psi).
To have a decent water production 60- 80psi are needed.

How loud is a booster pump ?
Let's say compared to a canister filter ?
 
0.9 to 1.1 bar is particularly low, although it's only required that your water board supply you with a minimum 1 bar of pressure.
You'll need at least 2 bar (30 psi) to run most standard diaphragm booster pumps.
 
0.9 to 1.1 bar is particularly low, although it's only required that your water board supply you with a minimum 1 bar of pressure.
You'll need at least 2 bar (30 psi) to run most standard diaphragm booster pumps.
The E-Chen self-regulating booster pumps are a newer model pump which will automatically stabilise the outlet pressure at 70psi when the inlet pressure is between 10-40psi. The consistent output pressure gives the advantage of prolonged RO membrane life.
 
Correct re. the self-regulating although I do believe they still require a minimum of 2 BAR (30psi). If you look at the image of the pumps (EC-204-XXXA) you can see that they still say "Inlet Pressure: 30psi" - perhaps the label hasn't been updated to match the model but definitely worth considering.

Not sure re. noise level on a decibel scale but they give off something of a "low hum" so nothing too disruptive.

I missed your earlier comment re. the lifespan of the Vontron membranes, sorry!
We typically state that they last between 12-24 months (water quality dependant of course) and they're used in all of our RO systems (domestic and aquatic). I've never heard of them only lasting 1 month. I would suggest that's more due to user error.

If your incoming TDS before pre-filters is only 70-90ppm (very low for municipal water btw) then I would hedge towards the 18-24 month range.
Chemicals such as chlorine are the biggest killer of RO membranes so as long as there's adequate carbon filtration beforehand and they're back-flushed regularly then they should last a good while.
 
This was taken form your website:
1679925300065.png

 
Don't get me wrong, I'm just trying to get as much info as possible before I commit spending few good ££ :cool:

I have a HM inline TDS meter that measures about 70-80 ppm before the carbon filters and on very rare occasions I got readings of about 90. Our water is very soft.
Because I can't trust the water company reports, I'm running 2 Chlorplus cartridges followed by Lead removal carbon block (0.5 micron).

The output of this carbon filtration I was planning to feed into the booster pump and from there to 2 RO membranes in series to reduce the waste water.

I assume the waste output of the second membrane will need a flow restriction. What size ?

Re Vontron membranes, that very good new about life span. The price is very attractive.
Will certainly place an order.

Thank you
Gabriel
 
One more thing I forgot to ask.
The RO membrane has to be installed horizontal or can be installed vertical as well ?
 
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