Big Blue carbon filter vs. Backwash catalytic carbon filter

Users who are viewing this thread

randomwalk

New Member
Messages
19
Reaction score
0
Points
1
Location
Bay Area
I'm interested in a carbon filter ahead of my softener mainly to protect the resin from chlorine / chloramine, with the added benefit of generally better water. I live in San Jose and the chlorine level in my city water is not super high (1.53 ppm on average according to the water quality report).

I'm getting conflicting suggestions. One local (and seemingly knowledgeable) dealer recommends against a 1.0 cubic ft. backwash catalytic carbon filter because:

(1) higher initial cost, and would be expensive to change the carbon after 3 to 7 years.
(2) uses a lot more water due to the need to backwash (water is not cheap in my area)
(3) not very effective because a 1.0 cubic ft. filter can only have about 4 to 5 gpm flow rate if you want effective filtering.

I cannot fit a bigger backwash filter than 1.0 cubic ft. due to space limitations.

Instead, he recommends a Big Blue 20" cartridge carbon filter (he said I can buy a higher quality filter online) because:

(1) lower initial cost and lower ongoing cost (annual cartridge vs. rebedding the backwash filter)
(2) higher flow rate
(3) no need electricity or water cost to backwash.

He seems to think the Big Blue would be effective (enough?) for my situation.

Let me just add that he is not trying to sell me either carbon filters. In fact, he says I can buy my own Big Blue online for less than he'll sell it to me, then I'll just pay a small amount for him to install it (along with a softener). He also does not normally carry backwash carbon filter as he does not believe in it, but he can order one or I can buy my own, and he'll install it (along with a softener). So he's not trying to make any money off of his recommendation for Big Blue. This guy's father literally lives in my neighborhood so has very local knowledge.

What do forum members think? It seems people on the forum seem to not like Big Blue, but would like to understand the pros and cons. Thanks!
 

randomwalk

New Member
Messages
19
Reaction score
0
Points
1
Location
Bay Area
You know that cannot be right -- 4.5x20 vs 9x48.

Yeah, I'm guessing Big Blue is probably less effective at filtering given the same flow rate? I mean, let's say we have two showers going at the same time, with the dishwasher running. Would either system limit the flow such that the pressure would be low?
 

WorthFlorida

Clinical Trail on a Cancer Drug Started 1/31/24. ☹
Messages
5,727
Solutions
1
Reaction score
982
Points
113
Location
Orlando, Florida
Carbon filters are good at what is called polishing the water. It will not absorb 100% all of the chlorine as noted depending on the flow rate. The best place for a carbon filter is the cold water line under the sink(s). Carbon filters can come in two types, granular (preferred) and block. The block carbon type will plug up from sediments in the water and eventually restrict water flow. therefore, you do not get full use of the carbon capacity.
I do not know what the problem is with chlorine going through the softener? There are millions of them installed on city water systems without a chlorine problem.
 

Reach4

Well-Known Member
Messages
38,796
Reaction score
4,412
Points
113
Location
IL
Yeah, I'm guessing Big Blue is probably less effective at filtering given the same flow rate? I mean, let's say we have two showers going at the same time, with the dishwasher running. Would either system limit the flow such that the pressure would be low?
In the BB format, there can be granulated activated carbon (GAC) and carbon block. I am sure that the pressure drop with carbon block would be very bad. I don't know if the BB with GAC would have too much backpressure. The 9x48 tank would have very little backpressure and would have no problem supporting 2 showers and a DW.
 

Bannerman

Well-Known Member
Messages
4,795
Reaction score
768
Points
113
Location
Ontario, Canada
As per Ditttohead, 1 cuft of carbon will provide an effective service flow rate of up to approx 3 gpm. As a 20" BB cartridge contains approx 1/6 cuft of carbon, you can then appreciate why BB cartridges are usually not recommended for point-of-entry applications.

The service flow rate is not a physical limitation but is the flow rate which if exceeded, that quantity of carbon can no longer keep-up to effectively remove contaminants. Carbon can effectively remove many contaminants and will have a different service flow rating for each contaminate.

As regular carbon removes contaminate mostly by adsorption, that will require the water to have adequate contact time with the carbon. The same is true for catalytic carbon even as it functions both by adsorption and catalytic action. A greater amount of either carbon within a larger diameter tank will result in increased contact time and a greater service flow rate.

Chlorine can be rapidly removed by even a small amount of regular carbon, but chloramine is much tougher to remove, usually requiring a substantial quantity of catalytic carbon.

Regardless of the carbon type, a 1.5 tank of carbon will likely have a lifespan of 3-5 years before replacement is necessary whereas cartridges may require replacement every 1-2 months.
 
Last edited:

randomwalk

New Member
Messages
19
Reaction score
0
Points
1
Location
Bay Area
Thanks, all!

At this point, I am leaning toward either backwash carbon filter or just not having a carbon filter (and use 10% cross link resin to better withstand the chlorine).

If cost was not an issue, would it be correct that I should get catalytic carbon instead of regular GAC for a backwashing filter? It's not clear if my municipal water uses chloramine -- I'm guessing they do to some degree, but they don't say clearly on their website or reports. Their water quality reports say "chlorine".

I guess what I'm asking is: is catalytic carbon just a more effective version of carbon? They both do absorb the same contaminants, but catalytic just works better? Or do they filter different things and I should pick based on what they filter?
 

Reach4

Well-Known Member
Messages
38,796
Reaction score
4,412
Points
113
Location
IL
If cost was not an issue, would it be correct that I should get catalytic carbon instead of regular GAC for a backwashing filter? It's not clear if my municipal water uses chloramine -- I'm guessing they do to some degree, but they don't say clearly on their website or reports. Their water quality reports say "chlorine".
https://www.sjwater.com/customer-care/help-information/water-supply-faqs says they use both. So if you plan for chloromine, you should be ok for either.
 

ditttohead

Water systems designer, R&D
Messages
6,088
Reaction score
455
Points
83
Location
Ontario California
BB carbon filters have a very limited capacity and they are fairly expensive to replace. They may flow water at 10 GPM, but their effective flow rate is far less. Many of the companies I work with sell them for the sole reason that they get to replace them all the time for a decent margin. A backwashing catalytic carbon system would be a far better choice. The units only need to backwash about once a month and this water can simply be discharged to a lawn of you want. An 8x44 GAC filter is not highly desired but it is a little better than the BB.
 

Bannerman

Well-Known Member
Messages
4,795
Reaction score
768
Points
113
Location
Ontario, Canada
is catalytic carbon just a more effective version of carbon?
Short answer - Yes.

Catalytic carbon is regular carbon that has been modified to enhance catalytic function with no reduction to adsorption performance.

Since GAC will provide some limited catalytic action, GAC could be utilized to catalyze Chloramine to other, less harmful compounds, but the quantity of GAC would need to be at least 5X greater than Catalytic carbon so as to achieve similar performance. There may also be other undesired compounds in your water where enhanced catalytic action might be beneficial.

It's not clear if my municipal water uses chloramine -- I'm guessing they do to some degree, but they don't say clearly on their website or reports. Their water quality reports say "chlorine".
Chloramine is in reference to water sanitization using a combination of Chlorine and Ammonia. Chlorine is injected into the water stream before the ammonia so it's fairly simple for a water provider to expand the areas Chloramine is to be utilized after an initial trial in one limited section of the city.
 
Last edited:

Bannerman

Well-Known Member
Messages
4,795
Reaction score
768
Points
113
Location
Ontario, Canada
the carbon tank would be 8" x 44" instead of 9" x 48" because of space limits.

If your space limitation is height, you might wish to consider a manual backwash valve. A manual valve should be less costly and will likely require less height above the carbon tank compared to an automatic valve. Since carbon will probably require backwashing only on a monthly basis, you can decide if an automatic function is necessary, or if taking 15-20 minutes each month to manually perform the task will allow you to obtain a larger capacity system within your allotted space and budget.
 
Last edited:

randomwalk

New Member
Messages
19
Reaction score
0
Points
1
Location
Bay Area
If your space limitation is height, you might wish to consider a manual backwash valve. A manual valve should be less costly and will likely require less height above the carbon tank compared to an automatic valve. Since carbon will probably require backwashing only on a monthly basis, you can decide if an automatic function is necessary, or if taking 15-20 minutes each month to manually perform the task will allow you to obtain a larger capacity system within your allotted space and budget.

Thanks, Bannerman. The space limit is the tank diameter, not the height. I will definitely go with catalytic carbon since the carbon tank is limited in size, so I will put in the most effective filtering media.

Right now, I'm trying to decide if I should get a smaller softener (9x48 instead of 10x54) so that I can get a bigger carbon filter (9x48 instead of 8x44).

I just tested my water hardness using Hach 5-B and it came out 13 grains instead of what I had assume (18 grains). I guess it can change a fair bit over time. Right now, we use about 150 to 200 gallons per day. That might grow to say, 250 to 300 in 7 - 10 years when the kids grow older.

It seems like a smaller softener would be ok right now? I guess the drawback of a smaller system and more regeneration is just that it uses more water, right? The salt seems like it should be the same?
 

Bannerman

Well-Known Member
Messages
4,795
Reaction score
768
Points
113
Location
Ontario, Canada
Right now, I'm trying to decide if I should get a smaller softener (9x48 instead of 10x54) so that I can get a bigger carbon filter (9x48 instead of 8x44).
The 9" softener will contain 1 cuft resin whereas the 10" will hold 1.5 cuft.

I see a local distributor offering 1 cuft carbon systems in 8"X 44" tanks and 1.2 cuft in 9"X 48". Those tank sizes are usually appropriate for 3/4 cuft and 1 cuft respectively as each tank should be only filled 2/3 to allow adequate space for media expansion during backwash. With the increased quantity in smaller tanks, I suspect either the freeboard space will be much smaller so the backwash rate will be reduced below the usual recommended rate to restrict expansion or, the upper screen will be heavily relied upon to prevent the media from being backwashed to drain.

As carbon is usually sold in 1cuft and 0.5cuft quantities, unless your supplier builds many carbon systems so as to utilize fractional quantities in multiple systems, it will be likely you will receive 1 cuft of media regardless of whichever tank size you purchase.

it came out 13 grains instead of what I had assume (18 grains).
As your city obtains water from multiple sources, the hardness level arriving at your home can often change due to time of day demand, maintenance, season etc. The test is a snapshot of the hardness at that specific time so it is usually recommended to add 2-3 grains to the test result when programming the softener, to anticipate occasions when hardness will be higher and more softening capacity will be consumed.

I guess the drawback of a smaller system and more regeneration is just that it uses more water, right? The salt seems like it should be the same?
A 1.5 cuft softener will deliver 31.5K grains when regenerated with 9 lbs salt or, 36K grains using 12 lbs salt. A 1 cuft softener will require 15 lbs salt to deliver 30K grains.

https://terrylove.com/forums/index.php?attachments/resin-chart-jpg.53316/
 

randomwalk

New Member
Messages
19
Reaction score
0
Points
1
Location
Bay Area
The 9" softener will contain 1 cuft resin whereas the 10" will hold 1.5 cuft.

I see a local distributor offering 1 cuft carbon systems in 8"X 44" tanks and 1.2 cuft in 9"X 48". Those tank sizes are usually appropriate for 3/4 cuft and 1 cuft respectively as each tank should be only filled 2/3 to allow adequate space for media expansion during backwash. With the increased quantity in smaller tanks, I suspect either the freeboard space will be much smaller so the backwash rate will be reduced below the usual recommended rate to restrict expansion or, the upper screen will be heavily relied upon to prevent the media from being backwashed to drain.

As carbon is usually sold in 1cuft and 0.5cuft quantities, unless your supplier builds many carbon systems so as to utilize fractional quantities in multiple systems, it will be likely you will receive 1 cuft of media regardless of whichever tank size you purchase./

Practically speaking, is it a big problem that the carbon filter is too full (i.e., 1 cubic ft. in a 8x44 tank)? I saw that the proper amount should be 0.75 cubic ft. as well, which is why I was thinking of trading for a smaller softener so I can get a bigger (1.0 cubic ft.) carbon filter.


A 1.5 cuft softener will deliver 31.5K grains when regenerated with 9 lbs salt or, 36K grains using 12 lbs salt. A 1 cuft softener will require 15 lbs salt to deliver 30K grains.

https://terrylove.com/forums/index.php?attachments/resin-chart-jpg.53316/

What I was saying is that, say I pick the same salt level (e.g., 6 lbs / cubic ft. of resin) for a 1.0 or 1.5 cubic ft. softener. The amount of soft water generated is proportional to the amount of salt. Therefore, a bigger system does not save on salt.

But maybe a bigger systems saves on the amount of water used to do the backwash? The chart does not tell you how long you have to backwash the resin given the amount of resin, so I can't tell if that is proportional. If the amount of water spent on backwashing is also proportional to the amount of resin, then it seems maybe you don't save water either. ***

*** I can see that there would be some salt and water inefficiency from a smaller system / more frequent regenerations because the system does not wait until zero grains remaining to regenerate, so the "buffer" amount would be lost. Is this the only reason why you'd want a bigger system? So you don't waste the buffer amount as frequently?
 

Reach4

Well-Known Member
Messages
38,796
Reaction score
4,412
Points
113
Location
IL
*** I can see that there would be some salt and water inefficiency from a smaller system / more frequent regenerations because the system does not wait until zero grains remaining to regenerate, so the "buffer" amount would be lost. Is this the only reason why you'd want a bigger system? So you don't waste the buffer amount as frequently?
Mostly. At higher flow rates, a smaller softener can leak more hardness (SFR). But at common flow rates 1 cuft would do the job.

The SFR in gpm is: 1.0 cuft = 9 gpm, 1.25 = 10 gpm, 1.5' = 12 gpm
 
Last edited:

Bannerman

Well-Known Member
Messages
4,795
Reaction score
768
Points
113
Location
Ontario, Canada
The chart does not tell you how long you have to backwash the resin given the amount of resin, so I can't tell if that is proportional.
The typical Backwash and Rapid Rinse rate for a 9" softener will be 2.0 gpm, and 2.4 gpm for a 10" tank. BW is often 10 minutes for each BW cycle and 5 minutes for RR. Some controllers will be programmed to perform 2 BW cycles, especially when using a low salt setting.

Depending on the valve chosen, both systems will likely use the same injector which will Slow Rinse at 0.45 gpm for 60 minutes, to cause brine to be drawn at 0.38 gpm for only the time brine is remaining in the brine tank, usually the initial 15 minutes of that 60-minute cycle.

The Brine Fill volume will be conditional on the actual salt dose required as each 1 gallon will dissolve 3 lbs salt.

Since the BW & RR flow rate will be slightly higher for the 10" tank, each regen cycle will use a higher amount of water compared to the 9" tank, but water savings will usually result from fewer regen cycles needed each month/year due to greater usable capacity within the larger system.

For overall efficiency, while the usual recommended method to estimate the minimum softener size required is to calculate 7-days average hardness consumption and obtain a softener large enough to deliver that capacity while using an efficient salt and capacity setting, there is no harm if the system is somewhat larger and will require less frequent regeneration.

As per the linked chart, a 1 cuft softener will regenerate 21K grains capacity with a 6 lbs salt setting (3.5K gr/lb), or 24K grains while using 8 lbs (3K gr/lb).

Edit to add: The buffer (Reserve) is normally 1-day usage capacity. In a 1 cuft softener, 1-day capacity will represent a greater percentage of regenerated capacity compared to a 1.5 cuft softener. How much of the reserve will actually be utilized will vary each cycle, conditional on how much water is consumed between when regeneration is triggered, until regeneration actually occurs, usually at 2 am the next morning.
 
Last edited:
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks