No, a shower pump is not normally fitted to a Megaflo or any other mains-pressure unvented cylinder. The cylinder already delivers hot water at mains pressure, and Heatrae Sadia presents the Megaflo Eco range as hot water performance without the need for shower pumps or tanks. Weak flow from one of these cylinders usually comes from the incoming cold water supply or from the height of the shower above the cylinder. This page explains what a Megaflo needs on the supply side, what the water fittings regulations say about pumps on a mains supply in England and Wales, and what an engineer should measure before anyone suggests a pump.
Can you fit a shower pump to a Megaflo cylinder?
No, not in the way most people mean. A Megaflo or other unvented cylinder takes water straight from the mains, so a shower pump is not part of its design. Heatrae Sadia describes the Megaflo Eco range as giving hot water performance without the need for shower pumps or tanks. Outlet pressure is set by the cold water combination valve on the cylinder, at 3.0 bar on Megaflo Eco and 3.5 bar on Megaflo Eco Plus.
Boosting the mains side is regulated work. In England and Wales, a pump or booster drawing more than 12 litres a minute from a supply pipe appears in the table of notifiable installations in the Water Supply (Water Fittings) Regulations 1999. The water company must consent before the work starts. So this is a notifiable job, not a fitting you simply add to the pipework.
A weak shower on a Megaflo is usually a supply or height problem, not a missing pump. Have the incoming pressure and flow measured first. A pump fitted to a mains-fed system can breach the water fittings regulations if the water company has not consented.
Why is your shower weak when the Megaflo runs at mains pressure?
Weak flow from a mains-pressure cylinder normally starts at the incoming cold supply. Heatrae Sadia recommends a minimum supply of 1.5 bar (0.15 MPa) at 20 litres a minute for Megaflo Eco cylinders. Manufacturer installation guidance for unvented cylinders warns that outlet flows can be poor at those minimum figures when several taps or showers run at once. The cylinder itself is rarely the restriction: the Megaflo Eco SystemFit indirect data sheet quotes a maximum flow of 76 litres a minute, and the Eco Slimline indirect 70 litres a minute.
Height is the second common cause. Outlets above the cylinder lose roughly 0.1 bar for every metre of rise, so 10 metres costs about 1 bar. A loft shower fed from a cylinder on the ground floor therefore feels softer than the same shower downstairs. Pipe runs, bends and the shower valve itself take their share on top of that.
What do the water fittings regulations say about a pump on a mains supply?
In England and Wales, a pump or booster that draws more than 12 litres a minute from a supply pipe needs the water company's consent before installation. Regulation 5 of the Water Supply (Water Fittings) Regulations 1999 requires notice for the installations listed in its table, and such a pump connected directly or indirectly to a supply pipe is one of them. The company must not unreasonably withhold consent. It may attach conditions, and consent counts as given unconditionally if no reply arrives within ten working days.
The practical effect is simple. Anyone proposing to pump the mains feed to a Megaflo has to deal with the water undertaker first. These regulations apply to England and Wales; separate rules cover Scotland and Northern Ireland.
How much pressure must your water company supply to the house?
Water companies in England and Wales must maintain at least 7 metres of static head in the communication pipe, which is around 0.7 bar. Ofwat's guaranteed standards scheme sets that level, and a payment falls due if pressure drops below it twice within 28 days for more than an hour each time. Exceptions include necessary works on the network and drought.
Seven metres of head is modest. Ofwat likens it to filling a 4.5 litre container in 30 seconds at a ground-floor tap. That sits well below the 1.5 bar at 20 litres a minute that Heatrae Sadia recommends for a Megaflo Eco. Ofwat also notes that householders are responsible for the pipes, fittings and stop taps on their own property, and that the company can carry out pressure and flow tests.
Which hot water systems are shower pumps actually built for?
Shower pumps are built for vented, gravity-fed hot water systems. In a vented system the cylinder is fed by a cold tank in the loft, and pressure comes only from the height of that tank. That pressure is low, so a pump raises it at the shower. An unvented cylinder such as a Megaflo has no loft tank and works at mains pressure instead, which is why manufacturers describe moving from gravity-fed to unvented as a route to better shower pressure.
A power shower is a separate case. It has a pump built into the unit and needs stored hot water to draw from. On a combi boiler it will not work, because a combi has no cylinder. If two bathrooms are the real issue, see whether a combi can serve two showers at once, and what converting a vented system to an unvented cylinder involves.
Who is allowed to work on an unvented cylinder in England?
In England, an unvented hot water storage system may only be installed by a person competent to do that work. Approved Document G of the Building Regulations, requirement G3, also calls for precautions that stop stored water exceeding 100°C and for discharge from safety devices to go somewhere safe and visible. Where the installer is not registered under a competent person scheme for unvented hot water systems, the building control body must be told before installation. A registered installer self-certifies the work, and you receive a Building Regulations compliance certificate.
The controls on a Megaflo are not householder parts. The strainer, the pressure reducing cartridge, the expansion valve and the expansion vessel charge are checked and serviced by an engineer qualified for unvented systems. Gas work on the boiler that heats the cylinder sits under the Gas Safety (Installation and Use) Regulations 1998 as amended and belongs to a Gas Safe registered engineer. More detail on qualifications is in our guide to who can install an unvented hot water cylinder in England.
What should be checked on a Megaflo instead of fitting a pump?
Start with measurement, not equipment. Baxi puts average demand for a heat-only system at 15 to 20 litres a minute, which is the yardstick for what your supply should deliver. An engineer can work through the items below before pumps are discussed at all.
- Static pressure and flow rate measured at the incoming main, against the 1.5 bar at 20 litres a minute Heatrae Sadia recommends
- The size and condition of the supply pipe into the property
- The setting and condition of the cold water combination valve on the cylinder
- The air charge in the expansion vessel, which needs topping up periodically
- The height of each outlet above the cylinder, at roughly 0.1 bar lost per metre
- Cylinder size against how many outlets run at the same time
Intermittent dripping at the expansion valve often points to a lost charge rather than a pressure fault; our guide on why an expansion vessel loses its charge covers that. If the measurements show the supply is fine and the cylinder is the mismatch, replacement or resizing is the honest answer. Our Megaflo and unvented cylinder work begins with a free home survey and a written fixed price before anything is ordered.
Sources
- Heatrae Sadia – Megaflo Eco unvented cylinders
- Heatrae Sadia – Megaflo Eco Indirect technical data sheet
- Heatrae Sadia – Megaflo Eco SystemFit Indirect data sheet (max flow 76 l/min)
- Heatrae Sadia – Megaflo Eco Plus installation manual
- Baxi – unvented cylinder installation and service manual
- Worcester Bosch – cylinder installation literature (Part No. 1051705)
- Viessmann – how to increase your water pressure
- Water Supply (Water Fittings) Regulations 1999, regulation 5
- Approved Document G with 2024 amendments (England)
- Approved Document G – frequently asked questions
- Ofwat – water pressure and the guaranteed standards scheme
- Baxi – matching the right boiler to the right customer