Data Centers
Guide
Cooling Tower Side-Stream Filtration Guide
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Short answer
Cooling tower side-stream filtration continuously treats about 3–10% of recirculating flow, sometimes up to 20%, to remove suspended solids (US DOE FEMP). Cartridges of about 5–50 µm, often large pleated high-flow elements, or bags of about 5–75 µm (Fil-Trek) are common, and the right rating depends on your water, treatment program and downstream equipment. FilterBridge Supply is a Southern California supplier of side-stream cartridges and bags, with quotes within one business day.
Why towers need side-stream filtration
Cooling towers scrub airborne dust, pollen and debris from the air, and solids build up as water evaporates. DOE FEMP notes that most suspended particles in tower water are 1–50 µm. Left unfiltered, they foul heat exchangers and give bacteria places to grow. In data centers, condenser water serves the chillers and heat exchangers that support the cooling plant, so steady water quality matters.
How much flow to treat
DOE FEMP's guidance is 3–10% of recirculating flow, up to about 20% in dusty sites. Your water treatment provider or engineer sets the final number from tower volume, local air quality and cycles of concentration.
Cartridge options
| Option | Typical use | Notes |
|---|---|---|
| Pleated jumbo high-flow cartridges | Larger side-stream flows in few housings | e.g. HSC-170: 105 gpm recommended, 0.35–150 µm pleated polyester |
| High-flow cartridges | Larger side-stream flow, fewer change-outs | e.g. HHFC40-5: 6″ × 40″, 5 µm, inside-out flow |
| Standard cartridges (10"/20") | Finer polishing on smaller skids (about 5–50 µm) | 2.5" and 4.5" diameters |
| Filter bags | Coarse prefiltration and heavy solids (about 5–75 µm) | Available on request |
| Media or centrifugal separators | Alternative technologies | Not supplied by FilterBridge |
Very fine cartridge filtration (Xylem notes microfiltration down to 0.1 µm) usually needs a coarser prefilter ahead of it to get reasonable cartridge life.
Choosing a micron rating
- Start with what your water treatment program or engineer specifies.
- A coarser stage followed by a finer stage spreads the load.
- Watch differential pressure. Change filters at the pressure drop your system's maker or treatment provider sets.
- Each FilterBridge product page gives the rating type the manufacturer publishes.
Get a quote
Send your current part numbers or spec for a quote within one business day. Cartridges are sold by the case.
Questions and answers
What percent of tower flow should go through side-stream filtration?
DOE FEMP cites 3–10% of recirculating flow, up to about 20% in high-dust locations.
What micron filter is used for cooling tower side-stream?
Published ranges are about 5–50 µm for cartridges and about 5–75 µm for bags (Fil-Trek). Your treatment provider's spec governs.
Cartridges or bags?
Most data center side-stream systems we see use cartridges, often large pleated high-flow elements. Bags are mainly used for coarse prefiltration or heavy solids.
How often are side-stream filters changed?
When differential pressure reaches the limit your system specifies, not on a fixed calendar.
Can you cross-reference my current side-stream cartridges?
Yes. Send the part number. See how to cross-reference a filter part number.
Sources
Send us one part number. We'll take it from there.
No account, no minimum, no sales call required to get a number. Tell us what you buy today and we'll come back with available options and case pricing on what we can supply.