Commercial Pool and Spa Supplies
Mermade Filter Add-On, Backwash Sight Glass
Mermade Filter Add-On, Backwash Sight Glass
SKU:MF-BSG
Couldn't load pickup availability
The Mer-Made Backwash Sight Glass Add-On is an essential commercial piping accessory manufactured by Mer-Made Filter, Inc. Designed for direct installation in the backwash waste discharge line of single-vessel or stacked dual-vessel horizontal sand filter systems, this full-flow visual indicator provides aquatic operators with real-time optical verification of water clarity during the backwash and rinse cycles. It ensures operators backwash long enough to thoroughly evacuate captured particulate and organics without wasting heated, chemically treated pool water or sewer discharge volume.
The assembly is engineered for heavy-duty commercial aquatic service and is constructed either as a cylindrical spool piece with a high-strength transparent viewing cylinder encased in a protective external guard, or as a heavy-duty Schedule 80 PVC body featuring dual optical acrylic/tempered sight windows.
| Parameter | Specification |
|---|---|
| Accessory Reference | Mer-Made Full-Flow Commercial Backwash Sight Glass Assembly |
| Primary Function | Direct visual monitoring of effluent turbidity during backwash and filter-to-waste (rinse) cycles |
| Available Sizes (Nominal Pipe Size) | 3.0 in, 4.0 in, 6.0 in, 8.0 in, and 10.0 in (DN80 to DN250) |
| End Connections | ANSI Class 150 Flanged (Schedule 80 PVC standard) or Van Stone loose-ring flanges; IPS Socket-weld ends available on smaller sizes (3"–4") |
| Viewing Cylinder / Window Material | Heavy-wall high-impact Polycarbonate, clear cast Acrylic, or Borosilicate glass |
| Body & Flange Construction | Heavy-duty Schedule 80 PVC, CPVC, or Epoxy-coated ductile iron / bronze retaining hardware |
| Protective Shield / Guard | Slotted PVC outer cage or 304/316 Stainless Steel tie-rod / perforated metal protective guard |
| Gasket / Seal Material | EPDM standard (Viton / FKM optional for elevated ozone contact systems) |
| Maximum Working Pressure | 50 psi (3.45 bar / 345 kPa) continuous; rated up to 100 psi (6.89 bar) proof |
| Maximum Operating Temperature | 120°F (49°C) for PVC components |
| Internal Flow Design | Full-bore unobstructed flow path (no internal restriction or head-loss penalty) |
| Installation Orientation | Horizontal or vertical pipe run directly downstream of the backwash waste valve |
| Compliance / Standards | NSF/ANSI Standard 50, Model Aquatic Health Code (MAHC Section 5.7) |
The sight glass installs into the common backwash discharge manifold prior to the air-gap drain break. During the reverse-flow cleaning cycle, water passes through the transparent section: initial discharge runs heavily clouded and turbid with trapped pool debris, coagulants, and silt, transitioning to clear water as the bed expands and rinses clean, signaling the operator to terminate backwash and advance to the filter-to-waste/rinse mode.
Engineering & Dimensional Data by Size
| Nominal Pipe Size | Laying Length (Face-to-Face) | Flange OD | Bolt Hole Pattern | Approx. Shipping Weight |
|---|---|---|---|---|
| 3.0 in (DN80) | Approx. 10.0 – 12.0 in (254 – 305 mm) | 7.50 in (191 mm) | 4 x 5/8" holes on 6.00" BC | 8 – 12 lbs (3.6 – 5.4 kg) |
| 4.0 in (DN100) | Approx. 12.0 – 14.0 in (305 – 356 mm) | 9.00 in (229 mm) | 8 x 5/8" holes on 7.50" BC | 14 – 18 lbs (6.4 – 8.2 kg) |
| 6.0 in (DN150) | Approx. 14.0 – 16.0 in (356 – 406 mm) | 11.00 in (279 mm) | 8 x 3/4" holes on 9.50" BC | 22 – 30 lbs (10.0 – 13.6 kg) |
| 8.0 in (DN200) | Approx. 16.0 – 18.0 in (406 – 457 mm) | 13.50 in (343 mm) | 8 x 3/4" holes on 11.75" BC | 35 – 46 lbs (15.9 – 20.9 kg) |
| 10.0 in (DN250) | Approx. 18.0 – 20.0 in (457 – 508 mm) | 16.00 in (406 mm) | 12 x 7/8" holes on 14.25" BC | 52 – 68 lbs (23.6 – 30.8 kg) |
