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Inherited CarWash with purchase of a lube shop
- Thread starter DamandaKillion
- Start date
The Waterboy
Member
A couple of things to note about the RO pre-filter. (This applies to all brands and makes.)
Filter type: Most of the filters on car wash ROs are usually 2.5" diameter x 20" length, 2.5"x 10", or 4.5"x10" (often called Big Blue). Regardless of the size, you should always use a melt-blown type filter and they are typically made from polypropylene. NEVER use a pleated filter when there is a pump downstream. If the filter becomes clogged, the pleated filter can collapse and get sucked into the pump causing major damage. Stringwound filters are also not advised.
Pore size: 5 micron is the best overall pore size, although some units are built with two filters in series and are designed to have a 5 micron first and then a 1 micron. This is an ideal setup but most of the time on city water pressure there's too much of a pressure drop across a 1 micron filter. If you have this, just leave one filter canister (called a sump) empty and put a 5 micron in the other.
Changing frequency: Please just change these once a month, they are cheap insurance. You can get them shipped from Kleen-Rite for a couple bucks each. Some people will say change it when there is a 10 PSI delta, and this is good advice, but 99% of car washes don't have pressure gauges on both sides of the pre-filter (or at all). If the filter is dirty when you change it, you waited too long.
Other pre-treatment:
In addition to the pre-filter, all ROs are designed to be fed softened and de-chlorinated water. Hardness should always be less than 1 GPG (ideally 0-5 PPM) and free chlorine should be less than 0.2 PPM (ideally 0 PPM). Chloramines generally do not damage an RO membrane if the pH is in normal range but they can over time. RO membranes are expensive but if you take care of them, they will last for many years. If you don't, they will not.
A 5 micron filter is designed to catch anything larger than 0.00019685 inches in size, so just because it looks "clean" doesn't mean it's not full and done it's job. Your RO inlet water should be going through a carbon bed first, which can act like a 5 micron filter itself. The filter is there to catch anything that makes it through the carbon bed and also broken down carbon from the bed. For reference, the pore size of an RO membrane is roughly 0.0001 and 0.001 microns. This is so that only some of the water molecules (H2O) can get through and the rest goes down the drain along with all the dissolved solids (TDS). This is obviously a perfect scenario and not every pore size is within spec so some dissolved solids always get through. If you are showing 0 TDS on your permeate (product water) then your meter is wrong.
Filter type: Most of the filters on car wash ROs are usually 2.5" diameter x 20" length, 2.5"x 10", or 4.5"x10" (often called Big Blue). Regardless of the size, you should always use a melt-blown type filter and they are typically made from polypropylene. NEVER use a pleated filter when there is a pump downstream. If the filter becomes clogged, the pleated filter can collapse and get sucked into the pump causing major damage. Stringwound filters are also not advised.
Pore size: 5 micron is the best overall pore size, although some units are built with two filters in series and are designed to have a 5 micron first and then a 1 micron. This is an ideal setup but most of the time on city water pressure there's too much of a pressure drop across a 1 micron filter. If you have this, just leave one filter canister (called a sump) empty and put a 5 micron in the other.
Changing frequency: Please just change these once a month, they are cheap insurance. You can get them shipped from Kleen-Rite for a couple bucks each. Some people will say change it when there is a 10 PSI delta, and this is good advice, but 99% of car washes don't have pressure gauges on both sides of the pre-filter (or at all). If the filter is dirty when you change it, you waited too long.
Other pre-treatment:
In addition to the pre-filter, all ROs are designed to be fed softened and de-chlorinated water. Hardness should always be less than 1 GPG (ideally 0-5 PPM) and free chlorine should be less than 0.2 PPM (ideally 0 PPM). Chloramines generally do not damage an RO membrane if the pH is in normal range but they can over time. RO membranes are expensive but if you take care of them, they will last for many years. If you don't, they will not.
A 5 micron filter is designed to catch anything larger than 0.00019685 inches in size, so just because it looks "clean" doesn't mean it's not full and done it's job. Your RO inlet water should be going through a carbon bed first, which can act like a 5 micron filter itself. The filter is there to catch anything that makes it through the carbon bed and also broken down carbon from the bed. For reference, the pore size of an RO membrane is roughly 0.0001 and 0.001 microns. This is so that only some of the water molecules (H2O) can get through and the rest goes down the drain along with all the dissolved solids (TDS). This is obviously a perfect scenario and not every pore size is within spec so some dissolved solids always get through. If you are showing 0 TDS on your permeate (product water) then your meter is wrong.
Buckeye Hydro
Active member
I agree with Waterboy - "Recovery" and "Rejection" are two critical metrics when operating an RO system, and they are understood by very few car wash managers.
A little jargon to help understand this:
Feedwater: The water delivered to your RO system - after any pretreatment like a carbon tank or softener.
Permeate: the purified RO water
Concentrate: the reject water
RECOVERY is a measure of the percentage of feedwater that is recovered as permeate. You can use the two flow gauges on your RO system to calculate recovery:
Permeate flow / (Permeate flow + Concentrate flow)
(this formula assumes you are not recycling any of your concentrate)
In a perfect world, your RO system would have a 100% recovery - every drop of feedwater (which you pay for) would be turned into purified water. Unfortunately, that's not the nature of RO technology. Assuming you have soft, or softened feedwater, a recovery of 50% would not be uncommon. You can adjust your recovery using the needle valve on your concentrate flow. But be careful here... for example, 4" diameter membranes have a minimum concentrate flow of 3 gpm - so don't choke off the concentrate flow too much. The minimum concentrate flow will depend upon how your RO system is configured - check your manual; and the nature of your feedwater chemistry.
Recovery will decrease over time if your membranes are clogging with scale or are fouling. It's a good idea to have a data blanks in your Operator's Log for permeate flow (gpm), concentrate flow (gpm), and the calculated recovery.
REJECTION is a measure of the percentage of TDS in the feedwater that is not making it through to the permeate. Again, in a perfect world, you'd like the rejection to be 100% - but RO technology isn't perfect and commercial RO membranes typically are factory rated at 98+%. Cheaper/lower quality membranes often have a lower rejection rate. To calculate rejection you need to have TDS measurements of your feedwater and your permeate. To calculate:
1 - (permeate TDS/feedwater TDS).
So for example, if your permeate reads 2 ppm, and your feedwater reads 100 ppm, then:
1-(2/100)=
1-(0.02)=
0.98, or 98%
Rejection will decrease over time as your membranes age, and can fall off dramatically if the membranes have problems. It's a good idea to have data blanks in your Operator's Log for feedwater TDS (expressed in ppm), permeate TDS, and the calculated rejection rate. It's best to measure the permeate TDS with an inline meter, rather than testing the TDS of the water in your tank.
Russ
A little jargon to help understand this:
Feedwater: The water delivered to your RO system - after any pretreatment like a carbon tank or softener.
Permeate: the purified RO water
Concentrate: the reject water
RECOVERY is a measure of the percentage of feedwater that is recovered as permeate. You can use the two flow gauges on your RO system to calculate recovery:
Permeate flow / (Permeate flow + Concentrate flow)
(this formula assumes you are not recycling any of your concentrate)
In a perfect world, your RO system would have a 100% recovery - every drop of feedwater (which you pay for) would be turned into purified water. Unfortunately, that's not the nature of RO technology. Assuming you have soft, or softened feedwater, a recovery of 50% would not be uncommon. You can adjust your recovery using the needle valve on your concentrate flow. But be careful here... for example, 4" diameter membranes have a minimum concentrate flow of 3 gpm - so don't choke off the concentrate flow too much. The minimum concentrate flow will depend upon how your RO system is configured - check your manual; and the nature of your feedwater chemistry.
Recovery will decrease over time if your membranes are clogging with scale or are fouling. It's a good idea to have a data blanks in your Operator's Log for permeate flow (gpm), concentrate flow (gpm), and the calculated recovery.
REJECTION is a measure of the percentage of TDS in the feedwater that is not making it through to the permeate. Again, in a perfect world, you'd like the rejection to be 100% - but RO technology isn't perfect and commercial RO membranes typically are factory rated at 98+%. Cheaper/lower quality membranes often have a lower rejection rate. To calculate rejection you need to have TDS measurements of your feedwater and your permeate. To calculate:
1 - (permeate TDS/feedwater TDS).
So for example, if your permeate reads 2 ppm, and your feedwater reads 100 ppm, then:
1-(2/100)=
1-(0.02)=
0.98, or 98%
Rejection will decrease over time as your membranes age, and can fall off dramatically if the membranes have problems. It's a good idea to have data blanks in your Operator's Log for feedwater TDS (expressed in ppm), permeate TDS, and the calculated rejection rate. It's best to measure the permeate TDS with an inline meter, rather than testing the TDS of the water in your tank.
Russ
Roz
Well-known member
Uber interesting and great info to know to help newbies or old hands understand spot free terminology as well as how things work. I am guessing that Buckeye and Waterboy sell RO systems so feel free to append your contact info to your posts so anyone looking can contact you to discuss if they desire a new system or have questions (up to you).
While important to understand the one selling point most systems will use to differentiate themselves or the various systems one place offers is the overall production of Gallons Per Day (GPD). You want to have the right size unit for you location such that you are not straining it at max production most of the time. We calculated the most RO water we would need per hour if all 6 of our bays used RO at the same time for say 6-8 hours and still have a 10-15% reserve capacity. The cost difference between units is usually small in comparison to running dry and over the life of your carwash ownership that extra cost is minuscule.
While important to understand the one selling point most systems will use to differentiate themselves or the various systems one place offers is the overall production of Gallons Per Day (GPD). You want to have the right size unit for you location such that you are not straining it at max production most of the time. We calculated the most RO water we would need per hour if all 6 of our bays used RO at the same time for say 6-8 hours and still have a 10-15% reserve capacity. The cost difference between units is usually small in comparison to running dry and over the life of your carwash ownership that extra cost is minuscule.
Buckeye Hydro
Active member
Yep - some of the things that go into recommending a certain capacity RO (in gpd) include:
*minimum winter water temperature
*capacity factor (essentially how many hours of the available time do we want the RO to have to run to keep up with demand), and
*size of the storage tank.
The "Gallons per Day" system manufacturers state is what we call a "Nameplate Capacity" - the capacity before any real life constraints like cold feedwater temperature are applied. Only in unusual circumstances should you plan on getting the nameplate production from an RO unit.
*minimum winter water temperature
*capacity factor (essentially how many hours of the available time do we want the RO to have to run to keep up with demand), and
*size of the storage tank.
The "Gallons per Day" system manufacturers state is what we call a "Nameplate Capacity" - the capacity before any real life constraints like cold feedwater temperature are applied. Only in unusual circumstances should you plan on getting the nameplate production from an RO unit.
The Waterboy
Member
I agree with everything Buckeye/Russ said. Just to tag on some additional info to his last paragraph regarding pre-treatment:
Hard RO feed water will cause a drop in production (GPM) and an increase in system operating pressure.
Chlorinated RO feed water will cause an increase in production, a decrease in system operating pressure, but a drop in product water quality (higher TDS).
My company does sell and service water softeners and RO units but car washes are a tiny part of our business. We mainly work on much larger units for semi-conductor plants, food manufacturing plants, and lab/medical facilities that have ultra pure water systems. I came on here to find some information on reclaim units for a car wash customer and found a lot of great information so I stayed with the hopes that I could repay the community with my knowledge/expertise in water treatment.
Hard RO feed water will cause a drop in production (GPM) and an increase in system operating pressure.
Chlorinated RO feed water will cause an increase in production, a decrease in system operating pressure, but a drop in product water quality (higher TDS).
My company does sell and service water softeners and RO units but car washes are a tiny part of our business. We mainly work on much larger units for semi-conductor plants, food manufacturing plants, and lab/medical facilities that have ultra pure water systems. I came on here to find some information on reclaim units for a car wash customer and found a lot of great information so I stayed with the hopes that I could repay the community with my knowledge/expertise in water treatment.
Dan kamsickas
GinSan Technician
I wish more operators and dealers would accept this. Too many times it's taken as divine word and it's not. It's like the energy star ratings on appliances. If you really believe that new fridge is only going to cost $60 a year to run, I've got some ocean front property that you would probably love.............in Arizona. There are too many variables. It's just one of the reasons I also recommend over-sizing what you think you're going to need.
The Waterboy
Member
What Dan said!!
For example: the Filmtec TW30-4040 is rated for 2600 GPD. That is based on running for all 24 hours of the day, but that works out to 1.8 GPM. The manufacturer rates the flow based on the treated feed water being 70 degrees F. but it also has to do with pump output pressure, influent TDS and several other factors. In no situation ever is that membrane going to make 1.8 GPM. The typical output of that membrane with 150-200 PSI is about 1.2 GPM under normal conditions (with warm water). I have seen it as high as 1.5-1.6 but that is rare, but have also seen it down to 0.6 GPM in the winter (water is less viscous when cold).
That being said, most car wash ROs from my experience aren't even real RO units, they are cobbled together random equipment with no pressure gauges, flow meters or sample ports. There will be one or two membrane vessels mounted as high up on the wall as possible, a pre-filter that is impossible to get to, and the pump/motor is usually a leftover chemical feed pump thrown in there. (A softener that has never been tested for hardness and a carbon tank that hasn't been re-bedded in at least 5-10 years is also the norm.)
For example: the Filmtec TW30-4040 is rated for 2600 GPD. That is based on running for all 24 hours of the day, but that works out to 1.8 GPM. The manufacturer rates the flow based on the treated feed water being 70 degrees F. but it also has to do with pump output pressure, influent TDS and several other factors. In no situation ever is that membrane going to make 1.8 GPM. The typical output of that membrane with 150-200 PSI is about 1.2 GPM under normal conditions (with warm water). I have seen it as high as 1.5-1.6 but that is rare, but have also seen it down to 0.6 GPM in the winter (water is less viscous when cold).
That being said, most car wash ROs from my experience aren't even real RO units, they are cobbled together random equipment with no pressure gauges, flow meters or sample ports. There will be one or two membrane vessels mounted as high up on the wall as possible, a pre-filter that is impossible to get to, and the pump/motor is usually a leftover chemical feed pump thrown in there. (A softener that has never been tested for hardness and a carbon tank that hasn't been re-bedded in at least 5-10 years is also the norm.)
