Water-powered backup sump pumps (Liberty SumpJet SJ10, Basepump RB750): quick sheet with code notes

Covers: Venturi (water-jet) backup sump pumps that run on municipal water pressure with no electricity: Liberty SumpJet SJ10 series and Basepump RB750 / RB750-EZ.

Cross-checkedBrands: Liberty Pumps, Basepump3 components

City water flows through a venturi and drags sump water out with it, so the backup keeps working in a power outage with no battery to maintain. Limits: needs a reliable municipal supply at enough pressure (not a well, which stops when the power goes out), uses metered water while running, pumps less than an electric pump, and most codes require an RPZ backflow preventer that must be tested.

Safety first

Supply-line connection and backflow device installation are licensed plumbing work in most jurisdictions; check local code and permit rules.
Sump water is non-potable; never cross-connect without the required backflow protection.

How it works

A float valve opens the city-water line when the pit rises above the primary pump's on level. Water rushing through the venturi creates suction that pulls sump water up the discharge.

Output falls as lift rises and as supply pressure drops. Liberty's table at 40 psi shows about 15 gpm at 4 ft of lift and about 7 gpm at 15 ft. Basepump rates the RB750 at about 750 gph at 10 ft lift and 60 psi.

Because it depends on house water pressure, it does nothing on a private well during a power outage (the well pump is down too).

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

Liberty Pumps residential products

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Newly installed sump pump sitting in a basement sump pit by Famartin, CC BY-SA 4.0

Diagnostic guides for this appliance

Guide · Sump / Well Pump

Sump pump service: pour test, float, check valve, discharge, pit cleaning and backup

Zoeller's instructions for common submersible sump pumps call for clearing debris from the basin and testing the system at least every three months; service companies agree on a quarterly pour test, a twice-yearly check of the check valve and discharge, an annual pit cleaning and a 2-3 year battery change on backups. The core test is simple: add water, watch the float lift, the pump start, the water leave and the pump stop.

7 steps ~30 mineasy

Guide · Sump / Well Pump

Well pressure tank annual check: precharge, switch settings and cycle time

A bladder or diaphragm well tank holds an air charge that should sit about 2 psi below the pressure switch cut-in (for example 28 psi on a 30/50 switch, 38 psi on a 40/60). The charge can only be read with the pump off and the system drained to zero water pressure. A yearly check catches a slowly leaking charge before it short-cycles the pump. Water from the air valve means a failed bladder.

6 steps ~30 minmoderate

Guide · Sump / Well Pump

Water in the basement but the sump pit is dry

If the pit stays dry while the floor gets wet, the water is not reaching the drain system that feeds the pit; the pump is not the problem. Usual causes are surface water (grading that slopes toward the house, short or clogged downspouts, overflowing gutters), a pump discharge that dumps next to the foundation, or a basement with no perimeter drain tile tied to the pit. Also rule out condensation and plumbing leaks.

6 steps ~45 mineasy

Other sump & well pumps manuals

Manual · Sump / Well Pump

Basement Watchdog Combo systems (Big Combo CONNECT CITS-50, Combo CITE-33): quick sheet

Factory-assembled primary + 12 V battery backup sump systems made by Glentronics under the Basement Watchdog name: Big Combo CONNECT CITS-50 (1/2 HP cast iron primary, BWSP-A 'Special CONNECT' backup controller with remote terminal and USB port) and Combo CITE-33 (1/3 HP cast iron primary, simpler backup controller). Both use a caged dual-float switch with a blue piggyback 'Dual Float Controller' on the primary and a dual float on the backup. Current manuals are dated 2025; older units sold under the same names may have different controllers, so match the controller model on its label (for example BWSP-A) to the manual. Model and serial labels: on the back of the black backup control unit, on the blue piggyback controller, and on the primary pump nameplate. Battery is sold separately (Basement Watchdog recommends its BW-27AGM). Search terms: Basement Watchdog Big Combo, CITS-50, CITE-33, Watchdog combo beeping, Watchdog battery light, Watchdog fuse light, Basement Watchdog reset button.

7 components7 common failuresBasement Watchdog

Manual · Sump / Well Pump

Superior Pump residential submersible sump pumps (92250, 92341, 92572 and siblings): quick sheet

Superior Pump (Decko Products, Minneapolis) 120 V submersible sump pumps sold at hardware and home centers: 92250 (1/4 HP thermoplastic, tethered piggyback float), 92341 (1/3 HP cast iron, vertical piggyback float) and 92572 (1/2 HP fiberglass-reinforced thermoplastic, vertical piggyback float), plus siblings in the same owner's manuals: 92251/92255/92257/92260, 92330/92331/92335/92337/92342, 92351/92352, 92501/92507/92511, 92270/92272, 92370/92372, 92570. Last digit and switch vary by SKU; read the label on the pump body and the switch tag. Search terms: Superior Pump 92341, 92572 sump pump, Superior pump won't turn on, Superior vertical float switch replacement, Superior Pump piggyback switch.

6 components6 common failuresSuperior Pump

Manual · Sump / Well Pump

Liberty Pumps 230 and 450 series aluminum submersible sump pumps (237, 231, 233, 457, 451, 453): quick sheet

Liberty Pumps (Bergen, NY) polypropylene base / finned powder-coated aluminum motor sump pumps: 230-Series 1/3 HP (230 manual, 230-P with unmounted vertical piggyback switch, 231 integral wide-angle float, 233 wide-angle piggyback, 237 vertical magnetic float 'VMF') and 450-Series 1/2 HP (450, 450-P, 451, 453, 457 VMF). HV = 230 V versions; suffix -2/-3/-5 = 25/35/50 ft cord. Same installation manual also covers the 240-series 1/4 HP cast iron (not detailed here). Model, serial and manufacture date are on the pump nameplate; record them on the manual cover. Search terms: Liberty 237, Liberty 457, Liberty 230 series sump pump, Liberty VMF switch, Liberty sump pump won't shut off, Liberty sump pump airlock.

7 components6 common failuresLiberty Pumps