Re: Strange filter problem
Let's start with the basics. How large is the pump in hp? How about the plumbing in I.D? How old are the cartridges?
I have worked on these filters since the first 300sq. ft. models came out in the very early 90's. The manifold is the same in all of them. When ever there is 30 or more psi showing on the gage with nothing downstream ( a clog, non-booster pressure cleaner, etc.) to cause this pressure, the manifold will collapse as yours has done. Maybe not immediately, but it will happen.
You do need a new manifold. Don't replace it until the cause of the problem is found. You probably need new cartridges as well as there are most likely small cracks in the end where it sits on the manifold.
Since the manifold is cracked, your cartridges may not have been cleaned as often as they needed, your pump is too large, or both, are the best-guess candidate for what you see.
If the bands that surround the cartridges are broken or the fabric seems "hairy" you need new cartridges. If the pump is anything over 1 hp it is too large and needs to be downsized. Just my opinion, but it has worked for the past 16 years.
Re: Strange filter problem
The pump is 2 HP and the main plumbing is all 2". The plumber that installed the pool said that was required since I have a large pool/hot tub combination. The pool has 2 skimmers, 5 returns...the cleaner is a suction cleaner. There is a heater in line but most of the time water is not diverted to the heater, it is mostly used for hot tub which has 6 jets and 2 returns to the hot tub.
One way that I could see this happening is running the hot tub only when the filters were dirty, we did that this winter a couple of times. It was always done at night and I wasn't paying much attention to pressure. But if it holds true with the 10 psi increase I usually have when filters get dirty, it could have been in the 35 psi range.
Under normal conditions when the pool returns are run the filter runs at ~12 psi. When using the hot tub only it runs at ~25 psi. As part of trouble shooting this, which I have done twice now, I tried using the different returns to test for clogs, etc. At first it all seems to work normally, none of the settings seem to increase pressure any more than normal such that it would indicate a problem in the line. As time goes on it always increases slowly, about 1/2 psi per minute until it gets up to 32-34 psi which it stays at until I clean the filters again.
The filters are ~2 years old, they look to be in pretty good condition. I generally clean them every 2 months normally, more often (every month) during the 3 months of heavy use and when the dog is shedding. Only 1 of the 4 filters has a frayed looking section on it. Do they make generic cartridges for these things? The local pool store and most of what I am finding only carry the very expensive Hayward branded ones.
Re: Strange filter problem
Try Unicell #C7488. They should cost about $60 - $85 each or even less.
You can try to chemically clean your existing cartridges.
I still recommend that you downsize the pump to 1hp. And, if you are going to let the dog swim in the pool, bite the bullet and put in a sand filter. Dog hair and dander do not mix well with cartridge filters.
Re: Strange filter problem
Actually the last time I cleaned the cartridges I did use the chemical cleaner. It still did not help. Same reaction when I put the cleaned filters back in.
The dog doesn't actually swim in the pool, she is a husky and she sheds twice a year and some of her hair ends up in a pool. The filters don't look horrible but there is usually a handful or two of hair when I clean it after a month of her shedding. Would a DE filter be ok with that amount of dog hair? I heard they are better overall...
Since it would be ~$400 for replacing all cartridges and manifold I am considering buying a new filter anyway. Plus that would help in the future because I really hate having to take this filter apart every 2 months, backwashing sounds easier.
Any idea if the manifold could cause that increase in pressure right away?
Re: Strange filter problem
It is possible that the manifold is collapsing enough to restrict water flow, especially since the middle support is also uncovered at the top.
D.E. is a good way to go. I have installed several of the new Sta-Rite Modular Media D.E. filters. Pentair, who now owns Sta-Rite, has one of their own also. They use a cartridge-type system instead of conventional grids. I also have not used D.E. in over 12 years, but a cellulose fiber substitute.
It is a much safer alternative to D.E. and keeps the water just as sparkling. If you decide to go with D.E. give it a try. Don't let yourself be talked out of it by people who have never used it or who have "heard" that it doesn't work. If you don't like it, go back to D.E. No, I don't own stock in any company that manufactures or distributes the stuff, it just works well.
I put it in all my new filter installs and have not had a single complaint. If you use it with a modular media type of filter, especially, cleaning is just a matter of opening the tank and hosing the cartridge off through the drain in the tank. The product, being all natural (it is a by-product of paper manufacturing) will usually disappear in a day or two. If you wash the debris down a drain, it won't clog it as D.E. will. A backwash valve can also be installed to these filters.
Much less mess, much easier to use. Just follow the directions on the package as to how much to add. It is about 1/8 the amount of D.E. that would normally go in the filter. A 7-pound bag is the equivalent of 56 pound of D.E. Costs a little more, but well worth it.
