Shower Pumps Buying Guide

A shower pump increases the flow and pressure of water reaching a shower on a gravity-fed plumbing system. On these systems, pressure comes only from the height of the cold-water storage tank above the shower head — roughly 0.1 bar for every metre of height — so upstairs bathrooms and loft en-suites often run weak because there is little height to work with. A pump is the right solution when you have confirmed a gravity-fed layout (a cold tank in the loft and a hot-water cylinder, typically in an airing cupboard) and the flow is poor despite the system working correctly. It is not a fix for a blocked pipe, a closed valve or a combi/unvented system. If you are unsure what system you have, check the loft for a cold-water tank before buying anything, and ask a qualified plumber to confirm.

Shower pumps are designed only for stored water on a gravity-fed system; they must not be fitted to a combi boiler or a mains-pressure unvented cylinder. UK water regulations prohibit pumping directly from the mains supply because it can draw down pressure for neighbouring properties and risk back-siphonage. A combi boiler has no storage tank or cylinder and delivers hot water on demand at mains pressure, so there is nothing for a pump to draw from. An unvented cylinder (such as a Megaflo) is already pressurised from the mains. On both systems the answer to weak flow is not a pump but a high-pressure thermostatic mixer shower, or addressing pipework and flow rate. Fitting a pump to either system is unsafe and non-compliant, so always confirm a gravity-fed layout before specifying one.

Head describes the pump's position relative to the cold-water tank, and it decides which pump you can use. With positive head, the pump sits below the level of the water in the cold tank, so gravity pushes water into it and it primes naturally; most ground-floor and standard upstairs installations are positive head. With negative head, the pump is at or above the tank's water level — common in loft conversions or where the tank is shallow — so gravity cannot reliably feed it. A negative-head situation needs a negative-head or universal pump, which senses the small drop in flow when the shower is opened and starts automatically rather than waiting for gravity pressure. A positive-head pump fitted in a negative-head position may fail to start. Salamander offers both positive-head and universal pumps; a qualified plumber can confirm the head type before you order.

The impeller count determines how many supplies the pump boosts. A twin-impeller pump has two separate impellers that boost the hot and cold supplies equally, delivering a balanced, properly blended temperature to a mixer shower — this is the usual choice for a whole bathroom and the safest for consistent temperature. A single-impeller pump boosts just one supply, for example a single feed to one shower outlet, and is suited to simpler installations where only one supply needs a boost. For most gravity-fed showers a twin-impeller pump is the right specification because it keeps hot and cold in balance as you adjust the mixer. Salamander offers both single and twin-impeller pumps across a range of bar ratings, so you can match the pump to the number of outlets and the supplies that actually need boosting.

The bar rating sets how much pressure the pump delivers, and you should match it to the shower's demand rather than simply buying the highest figure. As a guide, around 1.5 bar gives a gentle but noticeable boost suited to a single standard shower; 2.0 bar suits a more powerful single shower; and 3.0 bar or more is for powerful showers, large drencher heads, body jets or several outlets running together. A higher bar rating draws more water from the cylinder, so an oversized pump can empty a small hot-water cylinder quickly and may exceed what the tank and pipework can supply. Consider the cylinder capacity, the pipe size and how many outlets the pump serves before deciding. Salamander publishes the bar rating for each pump, making it straightforward to size against the bathroom's demand — a qualified plumber can confirm the right figure.

Two practical issues decide whether a pumped shower performs well: noise and air. Pumps transmit vibration, so mount the pump on a solid, level base, fit the anti-vibration feet supplied, and connect it with flexible hoses rather than rigid pipe to stop vibration travelling through the structure — this keeps running noise down, which matters when the pump sits near a bedroom. The second issue is drawing air: if the hot feed pulls air from the top of the cylinder the pump will gurgle, lose prime and may be damaged. To prevent this, the hot take-off should be a dedicated fitting such as a Surrey or Essex flange on the cylinder, which draws water from below the surface rather than skimming air from the top. Check the cylinder has a suitable take-off before fitting, and leave both the flange and the wiring to a qualified plumber and electrician.