By Kent Traders · Updated 20 October 2026 · 8 min read · UK
Most shower buying guides start with style. Start with the pipework instead. The same shower can feel superb in one house and weak in the next, and the water system is almost always the reason. Pick the shower for your water system first, then choose the finish.
Match the shower to how your water arrives. Combi and unvented systems run at mains pressure, so mixers, electric and high-pressure smart showers all work. Gravity-fed tank systems give low pressure, so choose a power shower or a gravity-pumped smart shower. Electric showers ignore your hot water system and need only a cold mains feed.
Which shower for your water system?
It depends on pressure and flow. Pressure is the force pushing water through the pipes. Flow is the volume that arrives at the shower. Lower pressure means lower flow, which is why the wrong shower on the wrong system feels weak. Aqualisa sets this out in its guide to which water system you are on, and the table below follows it.
| Water system | How it works | Pressure | Best-fit showers |
|---|---|---|---|
| Combi | Heats mains water on demand, no tank | Mains pressure; hot feed slightly lower than cold | Mixer, high-pressure smart, electric |
| Unvented | Mains-fed hot water cylinder | Higher than a combi hot supply | Mixer, high-pressure smart, electric |
| Gravity-fed | Loft tank feeds a hot cylinder below | Low | Power shower, gravity-pumped smart, electric |
How to tell which water system you have
You can usually work it out in five minutes without opening anything.
- Look in the loft. A large cold water tank plus a hot cylinder below it means a gravity-fed system.
- No loft tank, but a hot cylinder? A cylinder in an airing cupboard or utility room fed from the mains is an unvented system.
- No cylinder at all? A wall-hung boiler that heats water on demand is a combi.
- Still unsure? Check the boiler manual or ask your installer before you buy anything.
A small tank in the loft can be a feed and expansion tank for the heating. It does not make your hot water gravity-fed. Look for the large cold storage tank feeding a hot cylinder.
Gravity-fed homes: pumped showers
Gravity-fed systems rely on height, not the mains, to push water. That gives low pressure, and it is common in older houses. Aqualisa recommends two routes: a power shower, which has a pump built into the unit, or a smart digital shower, where the pump sits inside the SmartValve under the bath, in the airing cupboard or in the loft.
On product titles, GP means gravity pumped. Choose those. The Aqualisa complete showers collection includes several Quartz smart showers marked GP. Valves marked HP are built for high pressure and will likely disappoint on a tank-fed supply. Some bar valves are listed as LP/HP, so read the datasheet for the pressure range.
Combi and unvented homes: mixers and high-pressure smart
Combi and unvented homes run on mains pressure, so a pump is not needed. Aqualisa says mixer showers perform best here because nothing else is adding flow. Smart showers also come in high-pressure and combi versions, so you can choose a digital control without changing your plumbing.
One quirk applies to combis: the hot feed usually has slightly lower pressure than the cold, because the boiler needs time to heat the water. A thermostatic valve helps hold a steady temperature. Browse the shower valves collection and check each product page for its pressure requirement.
Do not add a pump to a mains-fed combi because the shower feels weak. Aqualisa says a combi can give a powerful shower without one. Check the valve, filters and supply first.
Electric showers: the system-proof option
An electric shower takes cold mains water only and heats it in the unit, so it works in any of the three systems. It needs enough cold mains pressure and its own circuit. All eight units in the electric showers collection are Aqualisa eVolve models in 8.5kW, 9.5kW and 10.5kW. Our kW guide in the related reading covers sizing, flow and Part P.
Worked example: four en-suites in a gravity-fed house
Take a house conversion with four en-suites, a loft tank and one shared hot cylinder. Compare two routes, with prices checked on 20 October 2026, including VAT.
| Option | Per shower | For four | Hot water use |
|---|---|---|---|
| Aqualisa eVolve 9.5kW electric (VOPZ26) | £321.54 | £1,286.16 | None from the shared cylinder |
| Aqualisa Quartz Blue Smart GP concealed (QZSB.A1.BV.23) | £567.73 | £2,270.92 | Draws from the shared cylinder |
The electric route costs £984.76 less on the units and leaves the cylinder alone. Each 9.5kW shower can draw about 41A, so check the consumer unit and supply first. The gravity-pumped route needs no new circuits, but four showers at once may strain the cylinder. For a landlord, the cylinder is often the deciding factor.
Where shower choices go wrong
Five mistakes account for most weak-shower complaints.
- Fitting a high-pressure-only valve on a gravity-fed system.
- Adding a pump to a mains-fed combi instead of finding the real fault.
- Mixing up pressure and flow, then buying a bigger shower head to fix a supply problem.
- Choosing finish before system, then discovering the valve is the wrong type.
- Assuming every digital shower needs high pressure. Smart showers come in gravity, combi and high-pressure versions.
What to buy: Aqualisa picks and stock
Prices include VAT and were checked on 20 October 2026. Of the 21 products in the Aqualisa complete showers collection, 19 showed low stock, so check availability before you order.
| Shower | Suits | Price | Stock |
|---|---|---|---|
| Aqualisa Quartz Classic Smart, ceiling heads (GP) | Gravity-fed | £850.40 | In stock |
| Aqualisa Quartz Classic Smart, adjustable with bath fill (GP) | Gravity-fed | £1,070.82 | In stock |
| Aqualisa Quartz Blue Smart, concealed fixed wall (GP) | Gravity-fed | £567.73 | Low stock |
| Aqualisa Quartz Classic Smart, concealed adjustable and bath (HP) | Combi, unvented | £752.57 | Low stock |
| Aqualisa Midas 110 bar valve (HP) | Combi, unvented | £309.73 | Low stock |
| Aqualisa eVolve 9.5kW electric, white (VOPZ26) | Any system | £321.54 | Low stock |
Check these before you order:
- Your water system, confirmed from the loft or the airing cupboard.
- The GP, HP or LP/HP marking on the product title.
- Whether the unit needs hot and cold feeds, or cold mains only.
- The stock level shown on the product page.
FAQs
A power shower or a gravity-pumped smart shower, because both contain a pump that overcomes low tank pressure. An electric shower also works, since it takes cold mains water only. Avoid showers rated for high pressure only, as they will feel weak on a tank-fed supply.
Yes. Aqualisa says mixer showers perform best on high-pressure or combi systems because there is no pump adding flow. On a combi the hot feed is usually slightly lower in pressure than the cold, so a thermostatic valve helps hold a steady temperature.
GP stands for gravity pumped. Those showers are designed for tank-fed supplies and include a pump. HP means high pressure, for combi and unvented systems. Some valves are listed as LP/HP, so check the product datasheet for the pressure range before you buy.
Usually not. A combi takes water straight from the mains, so Aqualisa says it can give a powerful shower without an additional pump. If the shower feels weak, check the supply, the valve and any blocked filters before you spend money on a pump.
Yes, because it heats cold mains water itself and ignores your hot water system. It needs a cold mains feed, enough mains pressure and its own circuit. Our electric shower kW guide covers sizing, breaker ratings and Part P in England.
Pressure is the force pushing water through the pipes. Flow is the volume that arrives. Lower pressure gives lower flow. Tank-fed systems are the usual culprit, and a pumped shower is the fix. Also check the time of day and how many outlets run together.
Related reading
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