1. Should be .75 cu ft IF the softener was correctly assembled and installed. 2 & 3. At two people and 30 gpg you need about 3600 grains removed per day. 3/4 cube of resin @ 6 lbs of salt (actually about right) = about 18k capacity so regeneration should be every 5 days so you have to choose 4 days and be safe or 6 days and chance hardness leaking through when the resin is exhausted. I'd choose 4 days. 4. Fleck 5600SXT for you. If you fill the brine tank all the way up you invite bridging and mushing. Only keep enough salt in the brine tank to cover the water and visit your parents more often... they'll like to see you more often. Timer softeners are old technology and not near as efficient as on demand initiated softener control valves.

The beauty of a Fleck 5600 is that parts and tech info are readily available in lots of places. If you have the 5600 Econominder on demand metered control valve then you have one of the best all time selling control valves and they last for decades and decades providing reliable service. Start by clicking here for parts and how-to instructions and videos. Make your repairs and set the bypass valve to SERVICE. You need to find out your current water conditions. If there's iron in the water you may need resin cleaner. Set the 5600 according to the water conditions. Clean out the brine tank and add 5 gallons of water and cover the water with salt. Wait two hours and initiate a manual regeneration. When that regeneration is complete there will be water in the brine tank. Add two gallons of water and add salt to cover the water and wait two hours with no water use if possible. Then initiate another manual regeneration. Now the resin is as close to full hardness removal capacity as it's condition will allow and the correct amount of water is in the brine tank for the water conditions that you set the 5600 to. Add salt to cover the water and that's all. Check salt once a week and add salt to cover the water. If you think this is all beyond your capability then look in the Yellow Pages for an independent water treatment professional. There's always someone everywhere who services Fleck control valves. I'd avoid plumbers unless they assure you that they have water treatment experience. Many plumbers think this is easy and at plumber's prices you can make an expensive mistake.

Alice, thank you for all of the detailed information. I currently have a dual tank Kinetico Model 60 that is 17 years old and needs new resin but since it is a proprietary system the local dealer wants $600 to replace the resin. Would you recommend replacing the resin or purchasing a new Fleck 5600sxt which would not be much more expensive? FYI for those who made be reading this, I have come to the following conclusions based upon my research: 1. Fleck appears to be the most recommended and companies like 602ABCWater provides a 5600sxt with the 10% cross-linked resin. There are more Fleck water softener systems on the internet because the distributors/re-sellers are not limited to a territory and can sell from anywhere to anywhere in the US. 2. Clack distributors/re-sellers cannot sell outside of their territory so there are fewer internet/web offerings. Reduced competition appears to cause the Clack systems to have a higher price than the Fleck systems. 3. Hydrotech / Canature appears to be the primary provider for many of the private brand valves/controllers including the Discount Water Softeners-Genesis, the US Water Systems- Fusion NLT and the Quality Water Treatment-SoftPro. All three of these companies quote the same statistics that promote the "efficiencies" and "cost savings" of an Upflow system vs a Downflow system. These companies also offer a 10 year warranty on the controller compared to 5 years for the Fleck but reading other blogs, it would appear that a Fleck controller can last 15 or more years which would probably outlast your resin.

Yes I did. I know that a packed bed would perform better, but it is difficult to achieve for a residential application. Using a regular bed with a cycle where backwash follows the regeneration should still allow to recharge the sodium in a more efficient way with a better efficiency though, although the polishing effect at the end will be canceled by the following backwash. The backwash will also use some capacity, contributing to lowering the efficiency a bit. Systems such as the NSF-tested Hydrotech 89 (http://www.hydrotechwater.com/downloads/manuals/softeners/54577%20Hydrotech%2089%20Water%20Softener%20Manual.pdf) seem to use upflow successfully. Is the overall efficiency (considering capacity usage due to backwash, rinse, brine refill and reserve capacity) of the upflow configuration for this system better than the downflow configuration? I don't know for sure, as I have not seen NSF data for the downflow version. Is this overall efficiency actually worse than the downflow version? I would assume unlikely, but at least on my end (Canada), they don't charge a premium for the upflow configuration. What I like with the Fleck 5810 series is that switching between upflow and downflow only requires a different piston, switching the position of the injector and reprogramming. The Fleck 5800 series is similar, except for a different regulator cap which is also required. The XTR2 also supports variable reserve and is very flexible in general. The 5800 series is available in both the SXT and XTR2 versions. The price difference between the 5600SXT and the 5800SXT here seems to be negligible. The price difference between the 5800XTR2 and the 5810XTR2 seems also negligible, but it is double the price of the SXT version. So I agree that the XTR2 is quite a bit more money to pay mostly just for variable brining. There is no price premium for upflow vs downflow as far as I know though... Price wise I think the Hydrotech system is the least expensive considering that it has all the software features of the XTR2. It is backed by a 7 years warranty. It is a Canadian company, but it does not have the long track record of Fleck. The Hydrotech control valve does not look as sturdy to me, but it might not mean much. (Edit: So I just looked at the 5810SXT Fleck valve and it has all the features I want. Double backwash, variable brining, external relay. It is more expensive than the 5800SXT (+25%), but no where near the price of the XTR2 version. I don't know why I had missed it before. It is definitely the valve I want. I could not care less about a touch screen, in fact I prefer avoiding them) Besides the upflow vs downflow debate though, my questions 1 and 2 remain. Is a 13"x54" tank better than the default 12"x52" for a 2 ft3 system? A smaller, but higher diameter tank would be preferable I think, but they don't seem to be available (a 12"x60" for example). Also is a #00 injector suitable if I want a regeneration level of 3-4 lb/ft3 with 2 ft3 of resin? Thanks!