Project managers should specify regenerative media filters that precoat in a closed loop and filters that precoat in the filter mode as equals. All regenerative media filters are required to automatically regenerate or “bump.” The swimming pool contractor will have the option to what filtration system to provide.
PMs should use Nemato’s Atlas filter as the basis of design when completing the design data and mechanical room layout due to their larger size. MEP requirements for Neptune Benson’s Defender filter should be coordinated within the design team because it has greater electrical infrastructure requirements.
Regenerative media filters are NOT approved with manual valves because of the possibility of introducing media back to the pool if the valves are not sequenced properly.
Regenerative media (RM) filters are any filter system which reuses the media without the need for backwashing. The operation of the system follows the same mode as most other filters during filtration. Water passes through media to remove particulate matter.
*Filtration rates higher than 1.5 GPM/ft2 can be considered on a per case basis depending upon the expected pool use.
The pre-coat cycle is the default starting point for all RM filters.
The pre-coat loop is typically two (2) pipe sizes smaller (but not less than 3” or greater than 8”) than the pressure (return) pipe to the pool. THE PROJECT MANAGER NEEDS TO CONFIRM THE PIPING SIZE REQUIREMENTS WITH THE BASIS OF DESIGN FILTER MANUFACTURER.
The hair/lint strainers should be a full port strainer. NO eccentric reducers should be used at the strainers. Since the pre-coat tee is connected after the strainer and before the pump, an eccentric reduced strainer may cause cavitation or exceed the maximum suction piping velocity.
The RM filter media can be diatomaceous earth (DE), perlite, or cellulose. At this time CH is not recommending cellulose as an alternate filter media.
Perlite (purified volcanic ash) which has been approved by NSF for use in pool filters. Perlite does not require a solids interceptor and can be discharged directly into the sanitary waste. It has similar filtering characteristics to DE, but it is environmentally friendly. Cost is comparable to DE media as well as filtration results.
Perlite is not as effective as DE. Perlite is degraded after each bump cycle no matter what RM filter is used. (Even “clean” bumps degrade perlite.) The more bumping means that the more perlite will float in the filter (i.e. ineffective media) and the more media will clump together. The more the media clumps, the more that the precoat is inconsistent. Depending on the designed precoat thickness, you could very well expose some of the elements over time.
If insufficient perlite media is in the filter cloudy water conditions can occur.
Perlite has been used for years in municipal wastewater and other industrial applications. Historically, the pool industry has received the rejected perlite that is not good enough (i.e. inadequate perm ratings) for these other industries.
Neptune Benson calls for a perm rating (or Darcy ratings) of at least 1.7.
Nemato uses a media source that will supply perlite with a rating of 3.25. The higher the perm rating, the more voids the media will have in it to capture dirt, particulate, etc. resulting in better filtration and less clumping. This perlite is Tech-Flo 2000x provided by Industrial insulation. The other significant benefit of this perlite is that it has virtually no float.
The Defender system requires a periodic chemical cleaning to remove spent media and oil left on the elements. Depending on the filter loading and pool usage, this should be planned for at least one time per year. This process requires the filter system to be off-line 24 – 36 hours.
RM filters require clearance over the top of the filter for head removal and maintenance. The project manager should confirm that the minimum requirements for overhead clearance above the filter tanks are met.
Defender filters should be designed with a 10-12 psi differential (28 TDH) and a maximum of 32 TDH.
Some counties and states require pearlite to be separated and removed before backwashing regenerative media filters to sanitary. Check local codes regarding this requirement. When this is required a custom separation, screen to be manufactured by Neptune Benson. It is recommended the separation screen to be capable of filtering to 10 microns.
Illinois Department of Public Health (IDPH) has required the addition of a solid’s interceptor for any manufacturers Regenerative Media Filter. They state that if in the future the owner decides to change media, the system will be capable of handling either media.
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