The Megaflo Main 300 Litre Indirect Unvented Hot Water Cylinder (7912282) is a high-capacity, UK-manufactured stainless steel unvented cylinder designed to provide mains-pressure domestic hot water heated indirectly by a compatible gas, oil or system boiler. With a factory-fitted 3kW Incoloy 800 immersion heater for backup, this 300 litre cylinder is suited to large homes with three or more bathrooms, premium properties and installations with very high hot water demand.
Megaflo Main is the new name for the Main unvented cylinder range. This model replaces the Main 300 Litre Indirect Unvented Hot Water Cylinder (5135328). Supplied as two boxes: cylinder plus fitting kit (90001992).
The cylinder features a unique coil-in-coil heat exchanger with a 19kW rating for rapid heat recovery, while 50mm of factory-injected CFC/HCFC-free polyurethane foam insulation helps minimise heat loss. It is KIWA approved, Building Regulation G3 compliant and supplied with a 2-port motorised valve for primary over-temperature protection.
300L Capacity
19kW Coil-in-Coil
3kW Incoloy 800 Immersion
25-Year Inner Vessel Warranty
Maximum Flow
55 l/min @ 6 bar
Applications & suitability
Large Homes
The 300 litre capacity is designed for larger domestic properties with substantial hot water requirements.
Multiple Bathrooms
Suitable for homes with three or more bathrooms and higher simultaneous hot water demand.
Indirect Heating
Designed to be heated through the integrated coil-in-coil heat exchanger by a compatible boiler.
Premium Installations
A high-capacity solution for premium properties and projects requiring substantial domestic hot water storage.
Key specifications
| Product Code |
7912282 |
| Type |
Indirect Unvented |
| Nominal Capacity |
300 Litres |
| Height |
2065mm |
| Diameter |
Ø550mm (Cylinder) / 595mm (Base) |
| Weight Empty |
58kg |
| Coil Rating |
19kW |
| Coil Heat-Up Time |
47 minutes |
| Recovery Time |
35 minutes |
| Standing Heat Loss |
2.52 kWh/24h |
| ERP Energy Rating |
D |
| Operating Pressure |
3.5 bar |
| Expansion Vessel |
24 litre (Supplied) |
| Connections |
22mm Compression / ¾" BSP |
| Packaging |
Two boxes: cylinder plus fitting kit (90001992) |
Installation & compatibility
Boiler compatibility: Designed for indirect heating via a compatible gas, oil or system boiler connected to the cylinder's coil-in-coil heat exchanger.
Installation: The cylinder is supplied with a 24 litre expansion vessel, T&P relief valve, 2-port motorised valve, pressure reducing valve and factory-fitted controls. Installation should be carried out in accordance with applicable unvented cylinder requirements.
Design & performance benefits
300L High-Capacity Storage
Provides substantial stored hot water capacity for large properties and high-demand domestic installations.
19kW Coil-in-Coil Heat Exchanger
The stainless steel coil-in-coil heat exchanger provides a 19kW rating for indirect cylinder heating.
50mm Polyurethane Insulation
Factory-injected 50mm CFC/HCFC-free polyurethane foam insulation helps minimise heat loss.
Backup Immersion Heating
A 3kW Incoloy 800 immersion heater provides backup electric heating when required.
Additional installation features
Supplied Expansion Vessel
A 24 litre expansion vessel is supplied as part of the cylinder installation package.
Motorised Valve
A supplied 2-port motorised valve provides primary over-temperature protection.
KIWA & G3 Compliant
KIWA approved and Building Regulation G3 compliant, with CE marking as specified.
Ideal for
The Megaflo Main 300 Litre Indirect Unvented Hot Water Cylinder is ideal for large homes with three or more bathrooms, premium properties and domestic projects with very high hot water demand. Its 300 litre storage capacity, 19kW coil-in-coil heat exchanger, backup Incoloy 800 immersion heater and 3.5 bar operating pressure make it a high-capacity indirect hot water solution. It pairs with the Main Eco Compact System or Main Eco Elite System boilers for a complete domestic hot water installation.
At GetPlumb, we strive to provide reliable and cost-effective delivery options to our customers. Please review our shipping policy below.
🆓 Free Local Delivery (Orders £100 & above)
We offer FREE delivery on orders £100 or more
for selected local areas.
Eligible Postcodes Include:
- RG*
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- WD*, HA*, UB*, TW*, KT*
- W1* – W9*
- NW*, SW*
Delivery Time: 2–4 working days
Shipping Cost: £0.00
📦 Standard Shipping (Weight-Based Rates)
For orders that do not qualify for free delivery, standard
shipping rates apply based on total cart weight.
- For cart weight between 0–2 kg, the shipping cost is £4.50 with a delivery time of 2–4 working days.
- For cart weight between 2–24 kg, the shipping cost is £9.99 with a delivery time of 2–4 working days.
- For cart weight between 24 kg and above, the shipping cost is £60 with a delivery time of 2–4 working days.
🧱 Block Salt (Harvey’s) – Unit-Based Shipping
This rate applies only to Harvey’s block salt products.
- £7.99 is charged for every 3 items.
- The charge increases by £7.99 for each additional set of 3 items.
Examples:
- 1–3 items → £7.99
- 4–6 items → £15.98
- 7–9 items → £23.97
Delivery Time: 2–4 working days
📏 Large / Long Items (Length-Based Shipping)
For oversized items where the product length is 1.5 metres or more:
Conditions:
- Product length ≥ 1.5 m
- Cart weight ≤ 40 kg
Shipping Cost: £18.00 (flat rate)
Delivery Time: 2–4 working days
Collection from Store
Customers can also choose to collect their order from our store in
Reading, UK, at no additional charge. For any questions regarding shipping, please contact our support team at online@getplumb.co.uk.
