Strong flow at every outlet
Mains-pressure hot water means showers perform properly upstairs and downstairs, without a pump making up for gravity that was never there.
Plumbing · Basingstoke & north Hampshire
Unvented Hot Water CylindersIn Basingstoke —Mains Pressure At Every Outlet
Mains-pressure hot water supplied, installed and maintained so two showers can run at once without either one dropping — no loft tanks, no pumps, no waiting for the cylinder to catch up.
Gas Safe registered 593588 · 15 years qualified · £2 million public liability · one-year workmanship guarantee
At a glance
Mains-pressure hot water cylinders supplied, installed and maintained for strong flow at every outlet.
- Free survey and a written price, fixed once given
- 8am–5pm, Monday to Friday
- Out-of-hours emergency call-outs available
- One-year workmanship guarantee on every job
15 years qualified
Apprenticeship completed 2011
Gas Safe 593588
Registered engineer
F-Gas certified
Refcom REF1025590
£2 million cover
Public liability insured
Fixed quotes
Free, and fixed once given
Overview
What an unvented cylinder does, and why it replaced the loft tank
An unvented hot water cylinder is fed directly from the incoming mains rather than from a cold tank in the loft. Because it is pressurised at mains pressure, the hot water arriving at your taps and showers is at the same pressure as the cold — which is what produces a shower that behaves like a shower rather than a trickle governed by how high the loft tank happens to sit.
That single change removes a long list of the old system's problems: the loft tank and its overflow, the pipework losing heat in the roof space, the reliance on gravity for pressure, and the shower pump added to compensate for it. It also frees the loft, which is why unvented cylinders are standard on modern installations and on almost every renovation that touches the hot water.
The trade-off is that a pressurised vessel of stored hot water is a system that has to be installed and maintained correctly. It contains safety components — expansion vessel, pressure and temperature relief, tundish and discharge — that exist to manage stored energy, and they need annual attention rather than being fitted and forgotten.
Who it is for
- Households with two or more bathrooms where simultaneous demand is normal
- Anyone whose shower loses pressure the moment another tap is opened
- Properties converting from a vented, tank-fed system to a modern sealed arrangement
- Renovations and loft conversions where the loft tank is in the way of the plan
- Owners of existing unvented cylinders needing servicing, repair or replacement
When it is needed
- Hot water pressure is poor at upstairs outlets, particularly showers
- The cylinder runs out of hot water long before the household has finished with it
- There is a loft tank you would rather not have, or it has started causing problems
- The existing cylinder is leaking, or the discharge pipe is dripping at the tundish
- A new system boiler is being fitted and stored hot water is the correct specification
The cost of leaving it
What goes wrong with hot water systems that are left alone
An unvented cylinder has safety components with a job to do, and those components fail quietly. The expansion vessel loses its air charge over time, and once it has, every heating cycle pushes expanded water out through the pressure relief valve instead of absorbing it. You see that as intermittent dripping at the tundish, which most households ignore for months.
That dripping is not harmless. It means the relief valve is operating repeatedly, which wears the seat until the valve no longer seals at all, at which point you have a continuous discharge of heated mains water going down a drain and onto your bill. Replacing an expansion vessel is cheap; replacing a cylinder because nobody investigated the drip is not.
Old vented systems have their own escalating problems. Loft tanks are open to the roof space, which means dust, insects and eventually contamination. Tank overflows and ballvalve failures in an unheated loft are also a reliable source of the kind of water damage that runs through two floors before anyone notices.
And the ordinary daily cost is simply the one people put up with: a shower that drops the moment someone runs the kitchen tap, a second bathroom that is effectively unusable while the first is in use, and a household organising itself around the hot water instead of the other way round.
Common mistakes
- Ignoring a dripping tundish, which is a failing expansion vessel or relief valve giving warning
- Skipping annual servicing on a pressurised system that contains stored energy
- Fitting a cylinder sized for the boiler rather than for the household's actual hot water usage
- Assuming an unvented cylinder will fix poor pressure when the incoming mains flow is the real limit
- Having unvented work carried out by someone not qualified for it
Our process
How a cylinder installation runs
Measured, specified, installed and commissioned with the safety components proved.
01
Survey and demand assessment
Incoming mains pressure and flow rate are measured — the single most important number, because a cylinder cannot deliver more than the mains can supply — alongside outlet count, household usage patterns, available space and the discharge route.
02
Written fixed quote and specification
You get the cylinder size and type, the heat source arrangement, the pipework and discharge plan and a fixed price. Free to obtain, fixed once accepted. Where a direct or indirect cylinder, or a different capacity, changes the outcome, you see the options side by side.
03
Removal and installation
The old cylinder and, where applicable, the loft tank and its pipework are removed. The new cylinder is positioned and secured, primary and secondary pipework is run, and the expansion vessel, relief valves, tundish and discharge pipe are installed to the required route and termination.
04
Filling, testing and commissioning
The system is filled and pressure tested, the expansion vessel charge is set, relief valves are proved, and the operating and stored temperatures are set correctly. Everything is checked under real demand rather than assumed to work.
05
Handover and guarantee
You are shown the controls, the isolation points and what the tundish is telling you if it ever drips. The installation carries our one-year workmanship guarantee alongside the cylinder manufacturer's warranty, and you are told when the annual service is due.
Benefits
What you get out of it
Hot water that behaves the way the household actually needs it to.
Two outlets at once, without compromise
Stored hot water is what allows a shower and a bath, or two showers, to run simultaneously — the thing a combi boiler cannot do regardless of its output.
Loft space back
No cold water storage tank, no feed and expansion tank, no overflow, and no pipework losing heat in a cold roof space.
Sized for your household, not a rule of thumb
Capacity is specified from the number of outlets and the household's real usage, so you neither run out mid-shower nor pay to store water nobody uses.
Safety components proved and maintained
Expansion vessel, relief valves, tundish and discharge installed correctly, commissioned properly, and checked annually rather than left until something drips.
One engineer for the whole system
Boiler, heating and hot water designed and installed together, with Gas Safe registration 593588, £2 million public liability and a one-year workmanship guarantee.
In detail
Cylinder types, sizing, safety components and maintenance
The technical decisions that determine whether hot water is a solved problem or a daily irritation.
Indirect and direct cylinders
An indirect cylinder is heated by a coil carrying hot water from the boiler — the standard arrangement in any property with gas central heating and a system boiler. A direct cylinder heats the stored water with immersion heaters alone, which is used where there is no boiler or as a backup arrangement.
Twin-coil cylinders take two heat sources, which matters where a second input such as a future renewable heat source is planned. Specifying the coil arrangement at installation is much cheaper than changing the cylinder later.
Sizing: capacity versus recovery
Cylinder sizing is a balance between stored volume and reheat time. Too small and the household runs out during a normal evening; too large and you pay standing losses to keep water hot that nobody uses, and the reheat cycle takes longer than it needs to.
The honest inputs are the number of bathrooms, how many people use hot water in the peak hour, whether baths or showers dominate, and the boiler output available to reheat the cylinder. Those numbers, not a generic table, decide the specification.
- Mains flow rate and pressure measured at survey — the hard limit on delivery
- Number of outlets and realistic simultaneous demand
- Bath-dominant versus shower-dominant households, which changes volume needs
- Available boiler output for reheat, which sets recovery time
- Physical space, access route and floor loading for the cylinder itself
Safety components and the discharge arrangement
An unvented cylinder carries an expansion vessel to absorb the expansion of heated water, a pressure relief valve, a temperature and pressure relief valve, and a tundish with a discharge pipe routed to a safe, visible termination. These are not optional accessories — they are the system that manages stored energy safely.
The tundish is deliberately visible so that any discharge can be seen. A tundish that drips intermittently after heating cycles is telling you the expansion vessel has lost its charge; a tundish that runs continuously means a relief valve has failed to reseat. Both need attention rather than a bucket.
Mains flow: the limit nobody mentions in a quote
An unvented cylinder delivers hot water at mains pressure, which means it can never deliver more flow than the incoming mains provides. If the property's supply is poor, fitting a mains-pressure cylinder will disappoint, and the honest conversation is about the supply rather than the cylinder.
That is why flow rate and pressure are measured at survey. Where the mains genuinely cannot support the demand, alternatives such as an accumulator or a different system design are the correct answer, and saying so up front avoids an expensive disappointment.
Annual servicing and common repairs
Unvented cylinders need annual attention. The expansion vessel charge is checked and re-pressurised, relief valves are tested and proved to reseat, the discharge route is inspected, temperature controls and thermostats are verified and the immersion heater is checked where fitted.
The most common repairs follow directly from those checks: expansion vessel replacement, relief valve replacement after repeated operation, thermostat and control failures, and immersion heater replacement. Each is a modest job caught early and a much larger one left alone.
Where cylinders fit alongside the rest of the system
Stored hot water pairs with a system boiler, which is why cylinder work usually forms part of a boiler installation or a full central heating installation rather than sitting on its own. Specifying both together avoids the classic mismatch of a high-output boiler feeding an undersized cylinder, or the reverse.
We install and maintain cylinders across Basingstoke, Hook, Hartley Wintney, Tadley, Andover, Kingsclere, Overton, Micheldever and Aldermaston, including in older properties where the change from a vented, tank-fed layout involves reworking pipework that has been extended piecemeal over decades.
Unvented hot water cylinders across Basingstoke and north Hampshire
Questions
Unvented hot water cylinders
answered straight
Anything not covered here, call 07825 758511 and ask. 8am–5pm, Monday to Friday, with out-of-hours emergency call-outs available.
How much does an unvented cylinder installation cost?
It depends on the cylinder size and type, the pipework and discharge route, and whether an old cylinder and loft tank need removing. Every job is surveyed and given a free written quote that is fixed once issued.
What is the difference between vented and unvented hot water?
A vented cylinder is fed by a cold tank in the loft and relies on gravity for pressure, so upstairs outlets are weak. An unvented cylinder is fed directly from the mains and delivers hot water at mains pressure, so showers perform properly on every floor and the loft tanks disappear.
What size cylinder do I need?
It depends on the number of bathrooms, how many people draw hot water in the peak hour, whether the household takes baths or showers, and the boiler output available to reheat it. The survey establishes those figures rather than applying a generic rule.
Why is water dripping from my tundish?
Intermittent dripping after the cylinder heats usually means the expansion vessel has lost its air charge. Continuous discharge usually means a relief valve has failed to reseat. Both should be dealt with promptly — a worn relief valve seat turns a cheap repair into an expensive one.
Do unvented cylinders need servicing?
Yes, annually. The expansion vessel charge, relief valves, discharge route, thermostats and controls all need checking. It is a pressurised vessel of stored hot water, and the safety components exist to be maintained.
Will an unvented cylinder improve my water pressure?
It delivers hot water at mains pressure, which is a substantial improvement over a gravity-fed tank. But it cannot exceed what the incoming mains supplies, which is why flow and pressure are measured before anything is recommended.
Can I run two showers at once?
That is exactly what stored hot water at mains pressure is for, provided the cylinder is sized correctly and the mains supply supports the flow. It is the main practical advantage over a combi boiler.
Can you replace my old vented cylinder and remove the loft tanks?
Yes. That is one of the most common jobs on this service — removing the cylinder, the cold water storage tank and the associated pipework, and installing a mains-pressure unvented cylinder in its place.
How long does the installation take?
A straightforward cylinder replacement is typically a day. Converting from a vented, tank-fed system involves more pipework and the removal of loft tanks, so it usually takes longer. The quote sets out the programme beforehand.
What guarantee do I get?
A one-year workmanship guarantee on the installation, plus the cylinder manufacturer's warranty on the unit itself. The business is Gas Safe registered 593588 and carries £2 million public liability insurance.
Next step
Get a fixed price for mains-pressure hot water
Free survey with your mains flow and pressure actually measured, and a written price that does not move. If your supply will not support it, we will tell you before you spend anything.
- Gas Safe registered 593588 · F-Gas Refcom REF1025590
- £2 million public liability insurance
- One-year workmanship guarantee, up to 10 years on new boilers
- 3 Mansfield Road, Basingstoke, RG22 6DU