Every pool must have a filter, if you don’t the pool is going to turn cloudy and green. The purpose of a filter is to remove particulate that form in the pool water. There are three types of filters on the market today. D.E. (an abbreviation for Diatomaceous Earth), sand, and cartridge. They all have pluses, they all have minuses. Today in class we are going to discuss D.E. filters.
When it comes to filtration you will not find a filter, on the market today, that will remove a smaller particle from the pool water. If you use Diatomaceous Earth in a D.E. filter, the filter will remove particles down to about 2 microns. A grain of sand on average is 100 microns, to give you a comparison. You can also use cellulose fiber in a D.E. Filter. Cellulose fiber filters just as well as D.E. but, has some advantages over D.E. First, it does not require as much cellulose fiber volume wise as D.E. Second, it backwashes better than D.E. And third, it is biodegradable, D.E. isn’t, D.E. is in its elemental form. There are a lot of localities that have banned the discharge of D.E. so cellulose fiber is an excellent substitute.
D.E. filters can be configured on a filter system several different ways. Some, in my opinion are better than others. One of the least common methods is to simply plumb the pipes into the filter and then out of the filter. That means when the filter is dirty and needs to be cleaned you have to take the filter apart and hose everything down. A messy job at best, hence this is my least favored method of hooking the filter to the system. If you currently have this type of setup, don’t despair, you can always upgrade your connection to make your life easier. I will discuss that in just a bit.
The next method is to use what is called a push/pull valve. This valve will allow you to easily backwash the filter by simply turning the pump off, then pulling the handle on the valve up, then turning the pump on again and running the pump until the filter is clean. Then you would turn the pump off and push the handle down, lock it then turn the pump on. Once the pump is on you will need to put more D.E. into the filter. How much you need to add we will discuss in just a moment. This, also, is not my favorite method of connecting the filter to the system because; it is very limited in what it can do. You have two options, either filter or backwash, that’s it.
The last method, my favorite, is a multiport valve. The multiport valve allows you to not only backwash the filter, it allows you to drain water without backwashing the filter (something you cannot do with a push/pull valve), it allows you to bypass the filter, and it allows you to stop the flow of water out of the filter when you turn the pump off and open the strainer lid on your pump. Proper operation of this valve requires you to turn the pump off before moving the handle to a different position on the dial.
If you have either no valve, or a push/pull valve you can switch to a multiport valve easily. All that is required is some re-plumbing, if you are not comfortable doing that type of work an Aegean Pools service technician can do that for you.
A D.E. Filter is a great filter, but not so great a backwashing device. Let me explain why; the way a D.E. filter works is the water comes into the bottom of the tank and is spread evenly inside the filter and over the grids inside the filter. When you add D.E. to the skimmer, by the side of the pool, the D.E. is delivered to the filter and the D.E. coats the grids evenly. As the water passed through the D.E. it leaves behind all the solid particles that will not fit through the D.E. As the D.E. gets clogged up with debris the pressure goes up on the filter tank. When the increase in pressure goes up ten pounds higher than the clean pressure you will need to clean the filter. Here I want to note that when you charge your filter with D.E. it is important that you make a note of the pressure reading because that is your baseline or reference pressure to determine when you need to backwash the filter. When we backwash the filter we are going to reverse that process filter process. The water will be entering the filter from inside, instead of outside, the grids. As this happens the D.E. is pushed off the grids and goes out the backwash line. If you are using a multiport valve to do this, you will watch the sight glass on the side of the multiport valve, when it is clear you will be done. Next, you want to turn the pump off (remember any time you change the position of the multiport valve you have to turn the pump off) and rotate the valve to the Rinse position. You then turn the pump on again and run the pump for twenty seconds. Next, you would go back to the backwash position again, this time for not quite as long, again waiting for a clear sight glass. You can repeat this process two times after the initial backwash. After you have done the backwash/rinse thing three times you have reached the point of negative returns and you should stop.
Your filter is now empty, well, almost empty. Remember, I said the D.E. filter is not a very efficient backwasher? Well, when the water enters the grid assembly during the backwash cycle it shoots straight down to the bottom of the grid. It usually misses the top four or five inches of the grid, so not all of the D.E. gets knocked off the grid. This said, if you put the full amount of D.E. that the manufacture calls for back in the filter you will end up with too much D.E. inside the filter and a higher starting pressure than normal. So I recommend you take one pound of D.E. off the recommended re-charge of the filter to compensate for the D.E. left in the filter.
For maintenance you need to take the filter apart once a season and clean it completely. D.E. will get caked up between the grids and not backwash out over the course of the summer. Taking it apart and hosing it down helps keep the filter working efficiently. You also want to, once a season, chemically clean the filter grids with BioGuard Kleen It® to keep the girds in top order so you get maximum flow through the grids.
There are nine rules of engagement for D.E. filters; I am going to list the top three rules for you today. For the other five rules, visit our store or visit our blog on Word Press:
Rule One – You NEVER run the DE filter without the DE powder in the filter.
Tip: if you need to circulate the water and you do not have DE in the filter, and you have a multiport valve on the filter, you may run it with the valve in the re-circulate position. This will bypass the filter. If you don’t have a multiport valve you cannot by pass the filter, sorry.
Rule Two – NEVER SKIP RULE NUMBER ONE.
Rule Three – Always use the proper amount of DE in the filter. This amount will depend on if you are backwashing the filter or you are taking the filter apart and cleaning it out completely. If you are taking the filter apart and cleaning it out you must use the full amount the manufacture indicates in the owner’s manual. If you are backwashing the filter take one pound off the manufacture’s recommendation and use that amount.
So that is everything you need to know about D.E. filters. See you next class.