Marine Pump Applications
Self-priming pumps for draining engine-room bilge wells, oily water and contaminated service water on all ship types. CTP bilge pumps are horizontal and vertical marine centrifugal designs with integral self-priming — no external priming system — so they hold suction as bilge levels fall. Tell us the vessel and duty data — we recommend the matching pump. Browse the full marine centrifugal pump range.
A marine bilge pump is the pump that drains the bilge wells and hold spaces at the lowest points of a vessel’s hull and machinery spaces — removing accumulated water, oily mixtures and contaminated service water so the ship stays stable, dry and compliant. Bilge duty is intermittent but unforgiving: the pump must start against a falling suction level, tolerate air and vapour, and handle water carrying oil, sediment and debris.
Because bilge wells drain below the pump inlet, self-priming capability is the defining requirement. The CTP EHS horizontal self-priming marine centrifugal pump meets it with an integral priming and air-separation structure — no external priming system — covering flows to 400 m³/h and heads to 150 m at speeds up to 3,550 rpm. Duty tables and technical documentation are available on our downloads page.
A ship’s bilge and drainage system calls on pumps differently by space and content. Three typical duties:
The main machinery-space bilge wells collect leakage, condensation and wash-down water. A self-priming centrifugal pump (EHS) drains them reliably as the level falls below the pump inlet.
Bilge water passes through the oily-water separator before any discharge overboard. The bilge pump feeds the separator at a steady rate and must tolerate the oil-water mixture without losing prime.
Where bilge and hold spaces carry sludge, sediment or viscous residues, a single screw pump (G / EH / ER / EU family) is the correct choice — see the eccentric helical rotor range.
CTP does not ask you to pick a model — send the vessel type and duty data, and we recommend the arrangement. For bilge service the starting point is the self-priming centrifugal range:
Where a non-self-priming centrifugal pump must be used on suction lift, CTP fits a self-priming device — the N-20 vacuum pump unit, or the EPS-200 / PSA-800 air ejectors (EPS-200 for suction DN ≤ 80 mm, PSA-800 above). Full specifications are on the marine centrifugal pump range page, or ask for selection assistance. For ballast duty on the same vessel, see our marine ballast pumps.
How the recommended series differ for bilge service:
| Series | Arrangement | Self-priming | Typical bilge role |
|---|---|---|---|
| EHS | Horizontal, end suction | Integral — no external device | Primary engine-room & general bilge on suction lift |
| TMS | Horizontal, self-priming | Integral — no external device | Daily service / sanitary; bilge & cooling standby |
| ESN | Vertical, two-outlet | With priming device | Combined bilge + ballast / sea-water & fresh-water |
| EHC | Horizontal | With priming device | Bilge & general service where flooded suction exists |
| VS / VS-S | Vertical, two-stage | With priming device | Fire & general service; bilge and ballast secondary |
“With priming device” means the N-20 vacuum pump or an EPS-200 / PSA-800 air ejector is fitted. The operating point within each series envelope is confirmed against your duty data. Source: CTP Pumps marine centrifugal pump selection manual.
Bilge water is abrasive and corrosive — sediment, oil and sea water together. The EHS is built around a double-volute casing that retains a priming charge, a built-in swing check valve on the suction side, and replaceable bronze wetted parts, so the same pump frame serves sea-water and contaminated bilge duty:
The numbered parts of the sectional drawing are listed below with materials for sea-water (S.W.) bilge duty. The built-in swing check valve (035) is what lets the EHS hold its priming charge without an external suction valve; the casing (001) retains the liquid volume used for re-priming.
| No. | Part | Material (S.W.) |
|---|---|---|
| 001 | Pump Casing | Bronze |
| 002 | Pump Cover | Bronze |
| 003 | Impeller | Bronze |
| 016 | Suction Cover | Bronze |
| 017 | Drain Cover | Bronze |
| 020 | Wear Ring | Bronze |
| 021 | Wear Ring | Bronze |
| 035 | Check Valve (built-in swing) | Stainless Steel + NBR |
| 050 | O-ring | NBR |
| 101 | Shaft | Stainless Steel |
| 103 | Impeller Key | Stainless Steel |
| 104 | Coupling Key | Carbon Steel |
| 120 | Impeller Nut | Stainless Steel |
| 124 | Impeller Washer | Stainless Steel |
| 161 | Wave Gasket | Carbon Steel |
| No. | Part | Material (S.W.) |
|---|---|---|
| 201 | Ball Bearing | Bearing Steel |
| 202 | Ball Bearing | Bearing Steel |
| 205 | Bearing House | Cast Iron |
| 209 | Bearing Cover | Cast Iron |
| 300 | Coupling | Carbon Steel + Rubber |
| 406 | Support | Carbon Steel |
| 501 | Packing | Carbonized Fiber |
| 503 | Lantern Ring | Bronze |
| 504 | Packing Cover | Bronze |
| 520 | Mechanical Seal | Seal faces: SiC + SiC |
| 521 | Seal Cover | Bronze |
| 522 | O-ring | NBR |
| 523 | Retaining Ring | Stainless Steel |
| 530/531 | Oil Seals | NBR |
Materials shown for sea-water (S.W.) bilge duty; fresh-water (F.W.) builds use cast-iron casing, cover, suction and drain covers. Other material combinations at request. Source: CTP Pumps.
Bilge pump selection starts from the vessel’s drainage system and the spaces to be served, not from a catalogue model. Provide the following and our engineers will recommend the pump, motor and sealing arrangement:
Pay particular attention to priming and NPSH: as a bilge well drains, the available suction head falls and air entrainment rises — this is exactly where a non-self-priming centrifugal pump loses prime. The EHS holds prime through these conditions by design. If you are unsure of the duty data, our pump selection assistance team will work through it with you.
Bilge drainage is a statutory safety duty — pumps and the bilge system are surveyed with the ship. Reference points that commonly apply:
Tell us the classification society and flag state at enquiry, and we will confirm the applicable certification route.
A self-priming centrifugal pump is the standard choice for engine-room and general bilge drainage. CTP recommends the horizontal EHS series as the primary bilge pump because it primes itself without an external priming system; the TMS and ESN series cover daily-service and combined-duty variants, and single screw pumps handle sludge-containing bilge.
Yes in almost every case. Bilge wells sit below the pump inlet, so the pump must lift and hold prime as the level falls. The EHS does this with an integral priming and air-separation structure and a built-in swing check valve. Where a non-self-priming pump is used, a N-20 vacuum pump or EPS-200 / PSA-800 air ejector is fitted to provide priming.
Oily bilge water is fine for a centrifugal bilge pump feeding the oily-water separator. Sludge, sediment and viscous residues are not — those duties go to a single screw pump (G / EH / ER / EU family). Tell us the expected solids content and we will split the duties correctly.
The EHS self-priming range extends to 400 m³/h and 150 m of head at speeds up to 3,550 rpm. Combined-duty and secondary series cover the rest of the envelope. Send your drainage plan and we will confirm the operating point.
Send the vessel type, spaces to be drained, required flow and head, suction conditions, media (clean / oily / sludge), power supply and classification society. You do not need to choose a model — our engineers recommend the pump arrangement against your duty data. Use the contact button below or our pump selection assistance page.
Send the vessel type and drainage data for your ship — we will recommend the pump model, materials and certification route.
Published by CTP Pumps · Source: CTP Pumps marine centrifugal pump selection manual · Last reviewed: September 23, 2026