150gpd FilmTec RO membrane

[braddo]

Many companies sell RO units equipped with FilmTec RO membranes. All the FilmTec membranes are the same physical size and are interchangable. (simple change in flow restrictor may be also be required)

The 50, 75 and 150 GPD membranes have the same rejection rate and output quality. (100GPD FilmTec membrane also available with lower rejection rate.) However it seems that none or very few RODI units are utilizing the 150GPD membrane. RODI units rated for 150GPD tend to use two 75GPD RO membranes in series. This is nice because it has less waste water output than a single 150GPD membrane.

My question is why would you ever want to use the 50 or 75GPD membranes when the 150GPD membrane is the same price, same size and same ammount of waste?

In the case of the dual membrane systems you would be making 300GPD with half the normal waste.

I've never heard anyone complain that their 75GPD system was making water too fast and they had wished they had gone with the 50GPD membrane instead. More often I hear the opposite, or stories like I turned on my RO filter, fell asleep and woke up to a flood.

 

[Myteemouse]

good question..
Watching this thread

 

[braddo]

I also posed this question to the support person at AirWaterIce.com. He skipped over the why is the 75GPD membrane the standard part of my question and simply said there is no problem replacing the 50GPD membrane in my MightyMite system with the 150GPD membrane.

I have a 150GPD membrane on order and will post results once it arrives.

 

[DolphinLVR]

good info!

I will be watching to see your results

 

[windwaterwaves]

I believe it has to do with the input pressure, according to the stats on bulkreefsupply and the 75's only need about 50psi, whereas the 150's need at least 65, so you may need a boost pump, but I agree the more water the better... I haven't checked my psi yet..

 

[braddo]

I think you nailed it with the 150 membrane requiring more pressure! I bet the 75's are used because they are less likely to have issues with standard household water pressure.

Our apartment has low water pressure that varies between 30 - 50 PSI. Whenever our pressure dropped below 50psi clean water production would drop substantially. In fact many times clean water output would be 0. We ended up purchasing a booster pump so water pressure shouldn't be a problem once the new membrane arrives.

I did a little googling on household water pressure, standards vary quite a bit. King County recommends 30 - 80 PSI.

http://www.sammplat.wa.org/pressure.asp

 

[Scooterman]

I use two filmteck 75's & I do have a high input of just about 80psi, which is within required range to get the high efficiency, which is why they go that route over the 150 membrane. Why pay to boost your water pressure if you don't need to?

http://www.thefilterguys.biz/dual_membrane_kits.htm

http://dow-answer.custhelp.com/cgi-...3RleHQ9cmVqZWN0aW9uIHJhdGU*&p_li=&p_topview=1

 

[sunny_mittu]

use 4 50 tech membranes instead of 1 150 tech...

more usefull and fast inflow/outflow

less wastage...