My guess is that he didn't have any underbedding in the softener.
I know you stated that this thread is for "people in here that have extensive field knowledge" and I am far from fitting that description but humor me if you will cuz I want to understand. Why would not the underbedding have kept the resin out of the bottom screen?
My guess is that he didn't have any underbedding in the softener.
The spider distributor is a great concept, but the percieved benefit and potential problems, and the extreme price make it difficult to recommend in a downflow system.
I finally fixed the picture, the final design has been working since January without a problem. I added in waste diversion based on TDS. The RO waste shares the same drain line which goes to irigation as well. I replaced my waste TDS monitor with a digital unit from HM Digital, and I added a 2 Cu. Ft. Post RO DI tank for my carwash and test sink. I have also added some more pressure gauges to see if there is any loss of flow through the system, so far, it is flawless. Obviously this is not exactly a marketable system but it does prove a few design ideas. It has no noticeable loss of flow through the medias with flow rates in excess of 15 PSI, and the backwash rate sharing through the different sized tanks works great with no loss of flow. The salt dilution is no issue condidering it only goes through an additional 10x22 tank prior to entering the softener tank.
All in all, I like the design, and the water it produces is great.
You are doing what I have been thinking. I just moved into a rental, after I build a custom house (less than a year away) I want a water filtration system much like this. Would you be interested in helping/sharing with me to design such a system. I do not know yet what my water will be like (well/city,etc). I have just recently become interested in water filtration technology, so I am way behind your knowledge, but I love this topic from an engineering perspective.
Feel free to post different systems/pictures of experimental systems you are involved with. Makes very interesting reading/learning.
FYI; I am a corrosion engineer for a super major oil company.
Thinking again after a Whataburger recharge. How are you figuring the tank diameter? The manufacturers seem to give a backwash rating of GPM as per cubic foot of resin? Are you using a cubic foot to mean a 12"x12" surface area or 144 square inches? Using the formula of pi times r squared to determine the surface area, a 10" diameter tank = 5" * 5" * 3.142 = 78.55 square inches. So 78.55" / 144" = 55% of the surface area. 55%* 15GPM = 8.25GPM.
But then, does converting a cubic foot to surface area the correct way to figure this? It seems to me the only correct way to figure this is by contact time. You need the water in contact with the media a long enough time to let the media do its job. So now we would need to figure the flow rate of the water in a given amount of volume. I just don't understand how you would convert a 3D volume to a 2D area.
My next brainstorm. Why as cheap as microprocessors are, there is no excuse for not using them.
My first question is where is the water meter turbine meter located? Is it able to measure all the water coming into the softener? If it can, why not use this to determine exactly how much water to put into the brine tank. I would think it would then also be possible to use a ratio from this to determine the same amount then pulled from the brine tank. This would eliminate unneeded time during these cycles. You could than also control the other steps (fast rinse, etc.) exactly. Why hasn't this been done?
I also need to find out would much salt can be dissolved in potable water. I expect a number of factors such as temperature, TDS, etc. will effect this. Anyone got a formula for me?
Is there an amount of contact time needed for the brine water to regenerate the resin? Many of the same factors would apply.
It also seems this process NEEDS to be controlled by a microprocessor (to get anything close to being called efficient) , even if you had to add a few inputs such as TDS, ORP and temperature. I think I might have a new hobby project.
Last edited by ByteMe; 11-11-2012 at 06:22 PM.
From Wikipedia, for pure water, for starters:
Substance Formula 0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C 80°C 90°C 100°C
Sodium chloride NaCl 35.65 35.72 35.89 36.09 36.37 36.69 37.04 37.46 37.93 38.47 38.99
Units of solubility are given in grams per 100 grams of water (g/100g). Conversion to pounds/gallon is left as an exercise for the student . Sorry about the formatting; the forum doesn't allow pretty formatting.
Some great questions and comments. First off, the backwash rates of most medias is determined by area, not volume. We calculate the square footage of a given bed area to determine the correct backwash rates. Density of media, specific gravity, surface area, water temperature etc all must be considered, but for the most part, the manufacturers of the media give us some fairly easy guidelines to follow.
Standard resin should be backwashed with 30% expansion. This would require approximately 10 GPM per square foot. Notice the chart below, it gives the temperature / bed expansion information allowing installers to easily adjust the system to the proper rates for the water temperature. Many problems have been caused over the years by companies not considering water temperatures in their equations. One of the largest restaurant supply companies hired me as a consultant about 20 years ago due to the high failure rate of their equipment, it was simply a lack of temperature compensation for their equipment. In the end we save them 100X my consulting fees in the first year.
As to volumetric calculations, we do that for some media, but not most. It is done typically to simplify the equations, but... surface area and bed depth are the preferred equations.
Activated Alumina, it has a recommended flow rate of... we simplify that to no ore than 3 GPM per Cu. Ft, that is assuming a bed depth of 30-36".
So many of these calculations rely on understanding the application. For a residential application, GAC and softening can typically be run at much higher flow rates than what the medias are technically supposed to be run at. On paper, GAC should not exceed 5 GPM per sq. ft., but we all run it at much higher flow rates, even when we are using poorly designed chlorine pellet systems. GAC can easily handle large quantities of Chlorine at high flow rates. On papaer, a common size 10x54 1.5 Cu. Ft. GAC system would have a manufacturer recommended maximum flow rate of 5 x 5 x 3.14 / 144 x 5 = 2.73 GPM. So a residential application that could see up to 10 GPM would technically need a 21" diameter tank system, or a 6 cu. ft. system. This is obviously not reasonable but on papaer it is the correct way to do it. We do many larger systems like this but they are for applications that require certifications to meet certain standards and the manufacturers literature must be followed.
This is where field experience and expertise become very important. Softeners exceeding their maximum recommended flow rate on an rare occassion has no real long term negative affect, otherwise every house that has four bathrooms would require a 5 Cu. Ft. softener.
I can definetly offer this system through one of our customers, we do not sell direct but we work with companies all over the world so it is definetly doable. I have had the best of luck with this design so far. Other than the failed Spider distributer, it is full proof so far.
Last edited by ditttohead; 11-12-2012 at 09:17 AM.