View Full Version : How much is too much?

03-22-2002, 06:59 PM

Hello, You have been very kind in the past to answer some of my questions. So I thought I'd ask another but here on The Canreef site to share with others. I was wondering if it's possible too have to much pressure to an ro system? If so how much is too much?

Thanks Jamie

[ 22 March 2002, 14:01: Message edited by: Jamie Cross ]

03-22-2002, 07:57 PM
Hello Jamie,

Thanks for the post. The Dow Filmtec low pressure membranes (which are the ones we use) can go to a max pressure of 125psi or .86MPa for you metric folks.

These membranes are rated at 50 psi, 77 degrees F, 250ppm softened tap water, pH of 8.

There are other membranes, such as desalinaztion types, that require high pressures. 600 PSI and higher are not uncommon.

I hope that answers your question, let me know if you need more information.


03-22-2002, 08:16 PM

Yes that helps. Thank you for the reply and quick responce.


03-22-2002, 10:01 PM
Originally posted by Marianne:

These membranes are rated at 50 psi, 77 degrees F, 250ppm softened tap water, pH of 8.

Marianne<font size="2" face="Verdana, Helvetica, sans-serif">Hi Marianne, just a quick question. you said max pressure was 125psi. my house presure is 150psi, PH 6.8, and my hardness is 20ppm. if I reduce my presure to 100psi would I get more than the rated amount out of the unit? so I guess I am wondering if I could expect more than 50GPD from a membrane you rate at 50GPD.


[ 22 March 2002, 17:03: Message edited by: StirCrazy ]

03-23-2002, 01:31 PM
This high pressure rating is to assure the membrane does not compress and get distroyed. These are low pressure membranes used so most households can generate RO water without the use of any addtional pressure (booster pumps).

You have a unique situation, most people's pressure is no where close to that. Dow is a very reputable company, I imagine their limits are conservative. It is best to stay in those limits thought.

Are you producing more than the rated flow now? I imagine you are. If you look at the membrane curves you will see the differences in flow rates the varibles make.


This URL (if it works) is the spec sheet. I think it is quite helpful


03-23-2002, 04:17 PM
Marianne, thanks there was a lot of info on that link.. I don't have a ro now but I am looking at buying one so I am looking at what size to buy.. from the info on thoes charts I think a 50gpd would suit me just fine..

thanks again

03-23-2002, 06:26 PM
Steve are you sure you're measuring your pressure correctly?

There is NO way that you have 150psi coming out of your lines. Perhaps you are getting 150psi service from the city/municipality, but there will be a regulator inline before your house plumbing to reduce that pressure to at least half of that.

I get ~45-50psi out of my kitchen tap (as measured on my RO/DI unit). I would suspect that your pressure is also somewhere in that ballpark, but I could be wrong?

If you are getting 150psi out of your taps, then you are really lucky man! That would be a kick-a$$ shower at your place! smile.gif

03-24-2002, 12:27 AM
trust me I measured it right.. smile.gif I was having problems with my safty on my hot water lifting all of a sudden.. I changed it and same peoblem. I guess the water company sent out a flyer saying resadents that don't have reducers on there lines need to install one befor a cirtin date.. well I bought the house after the letter and befor the date :( so my water pressure was bosted from 80 psi to 156psi (water heater safty valves start to lift at 110psi.. hehe) so I installed a reducer to bring the pressure down to 80 psi but my outside taps are still 150ish.. I love being able to water the whole lawn with out moving the sprinkler.. but I do have to buy a new sprinkler every month or two.. smile.gif


03-24-2002, 12:43 AM
it must be something funny about victoria cuz i get 125psi with a reducer coming into the house. its seems this is just below the threshold for the hotwater tank to start blowing by-passes!

03-24-2002, 12:46 AM
ya, the sook pump house cranked up the pressure about 4 years ago so people in sidny would have more than 40psi.. sence I am right off the main pipe line and only a couple miles from japan gulch (main pumping station..) I get the big time pressure.


04-06-2002, 03:14 PM
From what I have seen, most household pressure regulators are adjustable. (if you can find it ;) )

04-26-2002, 12:27 AM
Ok well I tested out my RO/DI, it has two 50 gps membrains on it so I should be able to push out 100 gpd.

the average I got was 86 GPD @80 PSI, 13.6 degrees C or 56.4 degrees F, TDS in was 29ppm and final was 0ppm. PH in was 7.1 and out of the DI it was 7.8
by looking at the tempature charts I am getting over the rated amount for that tempature so I guess that is good smile.gif next thing to buy is a high quality PSI regulator so I don't have to adjust my tap to get the 80 psi.