Hot Tub Water Filter

March 9, 2009 1:52 PM

There is fine iron sediment in my well water. My hot tub has a water circulating system that cannot tolerate filter blockage.

A service man told me that even minor filter blockage damages the pump seals. I do not have a piping circuit diagram for the tub and cannot describe how the filters operate in the system nor how the alleged differential pressure safety valve is supposed to function. There is a secondary filter that gets restricted after a few hours of initial use with iron buildup. The service guy told me that, even without my suspended iron problem, this secondary filter should not be in my, or in any other Coleman spa systems. Neither the filter packages or the spa owners manual have any micron specs for the filters.
All of this is just background for my question.

I need to be able to filter 300 gallons of water as the tub is filling and/or build a circulating filter that would be used before the main pumps are turned on. Filling the tub takes roughly about half an hour with no filtration. This is too large a volume of water for a household Ro filter to handle.

I have an unused small swimming pool filter system that could be used to either filter the water as the tube fills and/or use as a circulating filter before the circulating pumps are turned on. What is the smallest particle in microns that a sand filter can remove from water? I can also easily modify this system, if used as a circulating filter after filling, into a removable media filer.

I could also build a filter with stacked Scotchbrite pads. My parts washer uses a Scotchbrite polishing pad to filter sediment from the cleaning fluid.

Is it possible to use a hose mounted filter, such as the Gardenmate, that can be backflushed?

Any Form-Follows-Scrounge ideas?

posted by Raybun to home & garden (7 comments total)

Google says a sand filter is good for about 20-100 microns.

this secondary filter should not be in my, or in any other Coleman spa systems
This is confusing - you're not supposed to have the filter which is getting clogged? Can you remove or bypass it without hurting anything?

You might be able to read some part numbers off the filter in order to help to figure out its specifications - either to find inexpensive replacements or to know what sort of pre-filter you need.
posted by exogenous at 2:04 PM on March 9, 2009

How is the iron sediment getting pulled from your well? I have iron sediment problems mostly when a pipe is used intermittantly, or has been allowed to drain. The empty iron pipe is then able to rust, and the rust to dry out and turn to powder. Can you keep the pipes full, with a trickle flow?
posted by StickyCarpet at 2:26 PM on March 9, 2009

...Filling the tub takes roughly about half an hour with no filtration. This is too large a volume of water for a household Ro filter to handle...

Why not take a longer time, and send it through the RO filter? Does it matter that the tub takes all day to fill?

Can you get a Y-strainer, I've bought them down to 250mesh (60micron - industrial applications), and I'm sure you can get a finer mesh. Then when you fill, you periodically open the flush valve to dump some water and your iron stuff.

Also, you could try something like a big showerhead, suspend an old (clean!) towel across a bucket which you've cut a hole in the bottom, thus using the tower as a homemade filter. You probably won't get 10gpm through that though.
posted by defcom1 at 6:12 PM on March 9, 2009

Just thought of one more thing, can you use some sort of magnetic screen to pull the particles out? On the cheap a steel plate with a bunch of magnets hanging off the bottom, run the water over the top? With enough width you can run 10gpm no problem. 1-1/2" x 1" at 3.2 ft/sec., double the width for 1/2 the speed, or 1/2 the height.

Even, take another bucket (I like buckets), cut a hole in the bottom, or just put your hose on the bottom tied to a brick, attach your filling hose, put a lump of magnets (in a ziplock?) to collect your iron, let the water overflow the bucket into your tub?
posted by defcom1 at 6:26 PM on March 9, 2009

There is ferrous hydroxide in solution in my ag well. The water comes out of the well pale green and without anything precipitable in it. On exposure to air, the ferrous hydroxide oxidizes to ferric oxide, precipitating out as the red-brown powder.

This is commonly treated by an ozonator followed by a stilling pond or tank. Filtering this glop is really difficult.
posted by jet_silver at 7:51 PM on March 9, 2009

exogenous This was the advice of the service person who has seen a number of pump seal failures caused by the secondary filter being restricted.
posted by Raybun at 5:54 AM on March 10, 2009

exoenous again. You Google link led me to information on Diatomaceous Earth Type Filters. Thanks
posted by Raybun at 6:00 AM on March 10, 2009