Lee, if you went out and cleaned a cartridge filter and then backwashed and recharged a DE filter, it would make the decision very easy. Its hard for me to picture our customers disassembling the tank, cleaning all the gungy pleats, cleaning and lubricating the orings and reassembling the tank. They would be cussing me the whole time and end up hiring a service company. They would really be mad if the tank was breaking down and they imbedded all that fiber in their forearms.

We put 72 sq ft DE filters in all of our pools regardless of the pool size and as a result of the long cleaning cycles, many of our customers forget how to backwash between backwashes. I talk them through it on the phone usually and sleep better.

Renovxpt,

Thanks for that insight! What I'm worried about is the pressure that the DE filter has to operate at. If I'm correct, wouldn't I have to run my variable speed pump pretty fast in order to get the pressure in the DE filter to the correct point? That would defeat the purpose of a variable speed pump.

The only times you need to running at a substantial speed is at startup in the morning and during a backwash/recharge cycle.

Scott

Will you have solar heating? Solar heating will also require high speed.

Lee, to my knowledge there is no minimum pressure required to operate a DE or any kind of filter in the filter mode. As Scott stated the high speed is needed for backwashing. We have been using 2 speed pumps for many years and the low speed supplies enough flow to operate the cleaner and heater. The skimmers don't function very well on low speed. Primarily my customers use the low speed for winter use.

We use large cartidge filters if we install step and bench cleaning heads or certain water features. In these cases the cartridge is a secondary system to the main DE filter and rarely require cleaning because of their size. Usually we just replace the cartridges after a few years.

I would seriously question the builder that is pushing the cartridge filter.

Having said that, I have no actual experience with variable speed pumps but have read some of the intense discussions on this board about the pros and cons. IMO and practice we will continue to go with 2speed pumps until there is significant and time tested proof the variable speed pumps save enough energy and don't break down.

I just found the filter pressure loss charts in the instruction manuals of the FNS Plus DE series and the Clean and Clear Plus series cartridge filters and here are the numbers off the charts for the two types of filters:

FNS Plus DE series
30 gpm - .8 PSI
60 gpm - 3.2 PSI
90 gpm - 6.4 PSI

Clean and Clear Plus Cartridge series
30 gpm - .2 PSI
60 gpm - 1.2 PSI
90 gpm - 3 PSI

These numbers would certainly be for clean filters and clearly show that a cartridge filter has much less pressure loss, on a percentage basis, than a DE filter.

The statistic that I don't know about is how do these numbers change with a more typical semi-dirty filter in the two filter technologies, which type of filter gets dirty faster, and which type is more likely to be cleaned on a regular basis.

Also, for the .6 PSI difference between the two filters at 30 GPM or the 2 PSI difference between the two filters at 60 GPM, how much additional wattage is required to maintain that flow with the DE filter over the cartridge filter, with an Intelliflo pump? I'm sure that mas985 could answer that for us so we can all see to what extent the pressure loss difference matters.

First, are these two filters of equivalent size (not actual size)? Generally, a 60 sq-ft DE filter has about the same capacity as a 400 sq-ft cartridge. I know that sometimes the pressure loss does not depend on the filter size so maybe it doesn't matter.

If they are comparable in size, then the difference would only be about 10 watts to get to 30 GPM (925 RPM vs 990 RPM). These of course are estimates only and your results may vary.

BTW, I have a 420 sq-ft cartrdige filter on a 20k gallon pool and while they are a bit of a pain to clean, I only clean mine every 6 months (no closing) so it isn't so bad. It takes less than an hour to clean the four cartridges. Also, our city requires separation tanks on sand and DE filters which is why I ended going with a cartridge filter.

I personally don't have a lot of experience with DE filters but many on this forum and other forums have. One reoccuring theme is that the grids on DE filter occasionally get clogged and require cleaning. From what I understand, this can be a messy job and not too unlike cleaning a cartridge filter. Also, after every backwashing, they require more DE. My point is that DE filters may or may not require less maintenance than a cartridge. No filter is perfect and each has pro and cons. You basically have to pick your poison.

Also, what ever type of filter you choose, I would suggest that it is over sized so you don't have to clean it so often and so it cleans better.

This is why I love this board! I get different opinions and then I can use all the information to make the best decision I can. Thank you all for your input. I have received info from people that only do DE, people that only do cartridge and then people that don't care one way or another.

Personally, I'm going to go with a cartridge. I really want to make sure I can use my variable speed pump to the best of it's ability and don't want to have to worry about keep it running at a certain speed to get the filter working properly or started up. I also have a dog and I know that people say the DE disolves in the ground, but god forbid my dog drinks the backwashed water.... I just don't want to take that chance.

Thanks again for everyone's help!

Thanks for chiming in mas.

"First, are these two filters of equivalent size (not actual size)? Generally, a 60 sq-ft DE filter has about the same capacity as a 400 sq-ft cartridge. I know that sometimes the pressure loss does not depend on the filter size so maybe it doesn't matter. "

I believe that the graphs applied across the series as opposed to a particular model.

"If they are comparable in size, then the difference would only be about 10 watts to get to 30 GPM (925 RPM vs 990 RPM). These of course are estimates only and your results may vary. "

If that is all we are talking about in wattage difference then it is certainly not material to most people.

I have only used the cartridge filters and haven't found the cleaning process to be a big deal. It's just the cost of having a pool, the way I see it. Maybe I would feel different if I had used a DE filter.

Don't be so hasty Lee.

I would agree with Mas on 3 points.1.Separation tanks do complicate the ease of backwashing. The counties that put that requirement in place in our area have since repealed it long ago. 2.Bigger filters are better. 3. It takes an hour or less to clean a large cartridge filter.

However, it takes less than five minutes to backwash a DE or sand filter and you don't get wet in the process. If you figure the cost of replacing the cartridges $200+ every 4-5 years you have more than paid for the DE. Cartridge filters are touted as saving water because you don't backwash but if you measured the water used in the process of cleaning them it would probably be very close to the same volume.

After owning 2 pools for 40 years and installing and demonstrating the operation and cleaning of 1000+ filters of all kinds, I would rank sand as the simplest and most reliable and cost effective, DE second and cartridge lagging way behind in last place.

As stated in the first response. Invest an hour or so of your time to go thru the cleaning process for a least two kinds before you make the decision you will be living with the next several years.