RO water PH above 8.0 WTF?
- Thread starter Mongobud
- Start date
fatman7574
New Member
Let me rephrase the pH matter. A RO membrane does not produce pure water. A RODI filter does. With water produces by an RO membrane there are always extra H+ or OH- proportionaly. A pH meter responds only to a change in H+. With pure RODI water there are no excess or shortages of H+ to cause a reading other than a perfect reading of 7.0. With a RO membrane there is generally a great deal of CO2 in the finished water which cause readings that are lower than a pH of 7 initially and after aeration or sitting over night or so the excess CO2 is released from the RODI water and then that same water will read a higher pH of supposedly 7.0 There is also the possibility (very frequently) that H+ or OH- ions will be left in excess (inbalanced) by the RO membrane as these pass right trohgh the memrane after the attached ion (such as sodium or calcium) are seperated by the membrane. Unless you started out wih a pH of 7.0 you should not initaiily end up with a pH of 7.0 after the water has passed through the pH membrane. Few people have tap water with a PH of 7.0 because it is considered undesirable as it causes rapid piiting and rusting of steel pipe and dissolving of the lead in soldered copper pipes. Most tap water is in the high sevens or low just above 8 for a pH. Most water has had a great deal of soda ash (sodium Carbonate) added to it which is an alkaline carbonate. Any time you have hard water ie water with calcium carbonates that is run through a RO membrane you have calcium removed and it leaves behind the CO2. Therefore you have water wiy th a pH below 7.0 until that c CO2 is out gassed to the atmosphere. That is why when using RO water it should sit or be aerated before mixing up the nutrients because of the excess CO2.
There is s full process called lime softening that is done by many, many water treatment plants to lower the water hardness. In that process they add one form of calcium to increase the pH and to raise the dissolved calcium level (high enough that it comes out of solution and precipitates). Then the add soda ash so as to remove other calcium carbonates such as Magnesium calcium carbponate (an alkaline) to precipitae out. This leaves a huge excess of OH- ions in thw a water. These are not removed by a RO membrane, they must be removed by DI resins. So if your water provide by a treatment plant comes from wells instaed of a river or resrvior you likely have high levels of OH- in t your water after it runs through a RO membarnes so if your getting a reading of 7.0 it is only becuse you have excess CO2 in your water not beacuse your water will read a pH of 7.0 in a day or so after the CO2 has out gassed. With reaservoir or other surafce water it is common to have a pH below 7.0
A pH of 7.0 is common for water run through a RODI filter not water run through a RO filter. If your water comes out of a RO filter at 7.0 then likely it also entered the RO filter at 7.0 and the RO membrane had very little to even remove that the charcoal and particulate filters alone could not have handled. Most people with water coming from surface water sources do not need RO filters.
As far as the ridiculous comment about a steel hot water heater increasing the TDS level because it is steel and rusting. A hot water tank is glass or epoxy lined ans has a sacrificial anode,. The heating of the water actually lowers the TDS but it does increase the particulate level but prefilters remove that. Heating the water causes calcium carbonate (temporary hardness) to precipitate and it also causes dissolved iron and sulfur to precipitate. Precipitates are solids not dissolved solids. Dissolved solids t run through particulate filters such as prefilters. Particulates are captured by the prefilters before reaching the RO membrane filter.
Water tempeartures: All Cellulose Acetate style RO membranes are made to readily withstand temps up to 113 F. A typical hot water heater setting is 120 F , so a misture of hot and cold water is fine. While Thin Film membranes will tolerate higher temps for home owners the warranty is commonly voided by the manfacturers for temps above 113 F. They will however sell you what they call heat-sanitizable elements that can be heat-sanitized up to 85°C (185°F), meaning they warranty them for commercial use to temperatures of 185 F already but as a home owner you must pay extra for the same filter with a higher temperature warranty.
Applied membanes is the largest manafacturer of RO membarnes. Check here. http://www.watertreatmentguide.com/membrane_condition.htm
They are a bit deceptive, but basically a cellulose acetate filter which few home owners ever buy will not with stand temperatures above about 110 degrees F and a thin film membrane can withstand temps up to 185 degrees F. I have been using a mixture of hot and cold water ( average 95 degrees) with my RO membranes for over 10 years without problems. My tap water temp is seldom over 40 degrees which lowers RO membrane efficiency/performance a great deal.
There is s full process called lime softening that is done by many, many water treatment plants to lower the water hardness. In that process they add one form of calcium to increase the pH and to raise the dissolved calcium level (high enough that it comes out of solution and precipitates). Then the add soda ash so as to remove other calcium carbonates such as Magnesium calcium carbponate (an alkaline) to precipitae out. This leaves a huge excess of OH- ions in thw a water. These are not removed by a RO membrane, they must be removed by DI resins. So if your water provide by a treatment plant comes from wells instaed of a river or resrvior you likely have high levels of OH- in t your water after it runs through a RO membarnes so if your getting a reading of 7.0 it is only becuse you have excess CO2 in your water not beacuse your water will read a pH of 7.0 in a day or so after the CO2 has out gassed. With reaservoir or other surafce water it is common to have a pH below 7.0
A pH of 7.0 is common for water run through a RODI filter not water run through a RO filter. If your water comes out of a RO filter at 7.0 then likely it also entered the RO filter at 7.0 and the RO membrane had very little to even remove that the charcoal and particulate filters alone could not have handled. Most people with water coming from surface water sources do not need RO filters.
As far as the ridiculous comment about a steel hot water heater increasing the TDS level because it is steel and rusting. A hot water tank is glass or epoxy lined ans has a sacrificial anode,. The heating of the water actually lowers the TDS but it does increase the particulate level but prefilters remove that. Heating the water causes calcium carbonate (temporary hardness) to precipitate and it also causes dissolved iron and sulfur to precipitate. Precipitates are solids not dissolved solids. Dissolved solids t run through particulate filters such as prefilters. Particulates are captured by the prefilters before reaching the RO membrane filter.
Water tempeartures: All Cellulose Acetate style RO membranes are made to readily withstand temps up to 113 F. A typical hot water heater setting is 120 F , so a misture of hot and cold water is fine. While Thin Film membranes will tolerate higher temps for home owners the warranty is commonly voided by the manfacturers for temps above 113 F. They will however sell you what they call heat-sanitizable elements that can be heat-sanitized up to 85°C (185°F), meaning they warranty them for commercial use to temperatures of 185 F already but as a home owner you must pay extra for the same filter with a higher temperature warranty.
Applied membanes is the largest manafacturer of RO membarnes. Check here. http://www.watertreatmentguide.com/membrane_condition.htm
They are a bit deceptive, but basically a cellulose acetate filter which few home owners ever buy will not with stand temperatures above about 110 degrees F and a thin film membrane can withstand temps up to 185 degrees F. I have been using a mixture of hot and cold water ( average 95 degrees) with my RO membranes for over 10 years without problems. My tap water temp is seldom over 40 degrees which lowers RO membrane efficiency/performance a great deal.
Mongobud
Well-Known Member
So should I go get a "T" attachment for my RO, so I can run hot and cold water through it? Wouldn't that raise the psi and possibly damage the unit?
Regardless, I will let the RO sit overnight before using it. Thanks for the breakdown Fatman, you seem to know what you're talking about.
...now I just need to go get a float valve for it, before I get careless and my basement floods.
Regardless, I will let the RO sit overnight before using it. Thanks for the breakdown Fatman, you seem to know what you're talking about.
...now I just need to go get a float valve for it, before I get careless and my basement floods.
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Illegal Smile
Guest
I really don't see the problem here. ro water will not necessarily have a pH of 7, distilled will. The idea that you can't adjust or maintain proper pH in ro water is just false. The majority of the world's hydroponic marijuana is grown with ro water. Jorge Cervantes recommends it. So just adjust it and use it.
Mongobud
Well-Known Member
No problem bro, I'm new to RO, new to growing hydroponically, and used distilled all throughout the grow I'm in..about 24 days to harvest. I just got this RO system and I'm trying to understand it. I can Ph adjust it fine and after that it remains where a I wanted it. I was just curious as to why it fluctuated before adjustment, and if it was supposed to come out as 7.0 or not.
I'll grow regardless, I'd just like to use all of my equipment as effectively as possible.
I'll grow regardless, I'd just like to use all of my equipment as effectively as possible.
southern homegrower
Well-Known Member
why do u want to adjust the ph before u add your nutes
southern homegrower
Well-Known Member
mongobud that was meant for you
Mongobud
Well-Known Member
It's a new grow, no nutes. Just a drop of superthrive. I used FF entire line for my last grow. I always added nutes then adjusted PH.
That makes me think of something else though. I've never used GH nutes, but I recieved them with a new system. Do you adjust first then add nutes with GH?
That makes me think of something else though. I've never used GH nutes, but I recieved them with a new system. Do you adjust first then add nutes with GH?
southern homegrower
Well-Known Member
i always adjust the ph after i add nutes. i have only used gh nutes for about 2 wks. it had a lot of salt buildup. so i stopped using them. way to much scrubbing to clean for me
southern homegrower
Well-Known Member
my ph out of the tap is 7.5
fatman7574
New Member
You can readily adjust the pH of RO water. The problem is that the acciuracy of a pH reading right after the RO water is produced is not good as it can easily cahnge in amatter of a few hours. The pH does not need to be adjusted prior to mixing the nutrients but any excess CO2 should be driven off through aeration etc prior to its use. Excessive CO2 not only causes pH problems it also causes the formation of calcium carbonates., which tie up needed calcium and cause temporary false high pH readings and lead to plugged up misters, tubing and filters etc. It is best to run your RO water into a storage container and put a small aquarium power head in the tank pointed at the waters surface and let it run any time there is water in the storage vessel. As ;long as there is a ripple at the waters surface excess CO2 will be exchanged with oxygen. I use 32 gallon rubbermaid trash cans for small RO water storage containers.
fatman7574
New Member
Air pumps work fine, but they can be a bit noisy unless set on a mouse pad or suspended from rubber bands etc.
fatman7574
New Member
Some air pumps are quite, some are not. Some fans are quite, some are not. So do what you need to cut the noise. Vibratory noise seems to bother people. If an onjecy t is suspended from rubber that vibratory noise is not transfereed regardless of its source.
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Illegal Smile
Guest
My 600gph air pump is quite noisy. I suspend it with a bungee cord.