How to choose a pressure tank for a home water treatment system
How to choose a pressure tank for a home water system – complete practical guide
The pressure tank is the heart of every home water system. Without it, the pump would start every time a tap is opened, wear out in a fraction of its normal lifespan, and your pressure would be unstable. Despite this, the selection of a pressure tank is a mystery to many homeowners – I meet people who buy the first tank they come across and after a year face problems: too short pump running intervals, water hammer, overpressure or corrosion inside the tank. This article will help you avoid these mistakes and choose a tank that will serve without problems for decades.
What a pressure tank actually does and why it is essential
Before we move on to the selection, let's understand the basic principle. A pressure tank stores a certain amount of water under air (or nitrogen) pressure. When you open a tap, the water is pushed out by the air pressure until the pressure drops to the cut-in level – only then does the pump turn on. The pump then refills the tank and builds up to the cut-out pressure. Without a pressure tank, the pump would respond directly to pressure drops – meaning every time you open a tap, it would immediately start and stop, so-called short cycling or "ticking."
Ticking is deadly for the pump. Every time the motor starts, it draws a starting current five to seven times higher than the normal operating current, mechanical parts heat up and cool down alternately, and the windings break down. A pump designed for 10,000 to 20,000 starts in its lifetime will exhaust them in a few years instead of decades with ticking. A well-chosen pressure tank with sufficient capacity will dramatically extend the life of the pump and at the same time ensure a pleasant stable pressure when showering, in the dishwasher or when watering the garden.
Basic parameters that determine the choice
When choosing a pressure tank, you follow several key parameters. These are not just marketing figures – each of them has a direct impact on how your water system will behave in daily operation.
Volume of the tank
Volume is the first and most important question. Unfortunately, many people think that a larger volume = more water reserve, and buy, for example, a 200-liter tank for a small cabin with only one bathroom. This is unnecessary waste of space and money. On the other hand, a smaller volume than needed leads to too frequent pump starts.
Practical rule: for a typical family home with 4 people, one bathroom and a kitchen, where the pump runs at a pressure of 2.5–4.5 bar, a total tank volume of 24 to 50 liters is sufficient, with only 30–40% of that being usable water (the rest is occupied by air/bladder). For a house with two bathrooms, a dishwasher, a washing machine and garden irrigation, consider 80–150 liters. For family homes with higher consumption or for farms with agricultural use, 200–300-liter tanks are suitable.
The compact pressure tank Aqua OLA 24 l, horizontal is an ideal choice for small cabins, garden water systems or as an additional tank to an existing setup. For a pump with a power of around 0.5–0.75 kW and consumption by one person, it is sufficient without problems.
On the opposite end of the spectrum stands the galvanized pressure tank HVP 300 L or the stainless steel pressure tank CH 300 L vertical – these dimensions are intended for multi-generational homes, small businesses, guesthouses or places where you want a real reserve and the longest possible intervals between pump starts. A more detailed calculation of the volume according to the number of people, pump power and desired number of starts per hour can be found in the related article What volume of pressure tank do I need for my home.
Maximum working pressure
Each pressure tank has a stated maximum working pressure – typically 6, 8 or 10 bar. For home water systems with surface or submersible pumps operating in the range of 2–5 bar, a tank with a value of 6 bar is standard, sufficient and safe. Tanks for 6 bar are also cheaper due to the thinner wall, as they do not have to be dimensioned for extreme loads. However, if you plan to significantly increase the pressure (for example, for a multi-story house or special use), or if your area has high static pressure, go for a tank with a higher maximum pressure value.
Important: there is always a pre-set air pressure in the tank – usually 0.2–0.5 bar below the pump's cut-in pressure. If your cut-in pressure is 1.8 bar, you set the pre-charge pressure in the empty tank to 1.5 bar. This is the correct setting and it is essential to maintain it. More about setting the pressure can be read in the article What pressure to set in the pressure tank and how to check it.
Tank material – galvanized or stainless steel
This is a question that almost every customer asks. In short: galvanized steel is more affordable and has proven itself over time, while stainless steel is more resistant to corrosion and better suited for more aggressive water. A detailed comparison can be found in the article Galvanized vs. stainless steel pressure tank – which is better, but here we will only highlight the main points.
Galvanized tanks (such as HVP 200 L vertical galvanized) are the standard choice for ordinary well or surface water with medium hardness and neutral pH. The galvanized coating inside protects the steel from corrosion, but in more acidic water (pH below 6.5) or in very soft water, zinc starts to dissolve more quickly. The lifespan under normal conditions is 15–25 years.
Stainless steel tanks (for example, stainless steel CH 90 L) are resistant to a wide range of pH values (5.0–9.5) and are not sensitive to water hardness. They are the mandatory choice where the water is significantly acidic, where there is a higher content of sulfates or chlorides (for example, near the sea coast or in industrial areas), or where the customer requires absolute hygienic reliability without any risk of corrosion. The price is higher, but with problematic water, this investment pays off – and tanks with a stainless steel shell are often certified for potable water directly.
Construction – with or without a bladder
This is the second most common question. Tanks without a bladder (older type, membrane or direct contact of air with water) have air in direct contact with the water. Over time, the air dissolves into the water and the pre-pressure is lost – it must be regularly refilled. The advantage is a simpler construction and lower cost.
Modern tanks with a membrane bladder (butyl or EPDM rubber) separate the air and water. The air remains clean and does not dissolve into the water, so the pre-pressure remains stable for much longer. The bladder is replaceable, which extends the life of the entire device. For potable water, the bladder is made of food-grade certified rubber, which is a given. The article Pressure tank with a bladder or without a bladder – what is the difference describes this issue in more detail, including when it makes sense to choose the older type.
Tank orientation – vertical or horizontal
Tank orientation is more of a spatial issue than a technical one. Vertical tanks take up less floor space and are the standard for larger volumes – 90, 200 or 300 liters in a vertical position stand stably on legs and are easily accessible for inspection and service. Horizontal tanks, such as the mentioned Aqua OLA 24 l, are practical where ceiling height is limited (low basements, underfloor installations) or where you want to install the tank directly on the pump frame.
From a functional point of view, there is no difference between them – both orientations work equally well. If you have enough height, choose the vertical one – it is more stable, easier to connect the pipes to, and visually more organized. A more in-depth look at this topic is covered in the article Standing, lying or vertical pressure tank – which type to choose.
Vacuum material – what is butyl and why it matters
If you have decided on a tank with a vacuum (and this is the right choice for drinking water), you may be wondering what the vacuum is made of. The standard options are butyl or EPDM (ethylene-propylene-diene monomer) vacuums. Both are resistant to water and have food-grade certification, but they differ in details:
- Butyl vacuum – long-term resistance to air diffusion (air only passes through the vacuum wall minimally), good flexibility even at lower temperatures, typically 5–10 years with proper operation
- EPDM vacuum – more resistant to ozone and UV radiation (less important since it is inside the tank), slightly better resistance at higher temperatures
- Nitrile vacuum (NBR) – less common, used where trace amounts of oils or hydrocarbons are present in the supply
For regular well water, a butyl or EPDM vacuum is always the right choice. It is crucial that it is certified for contact with drinking water according to the relevant European standards – verify this in the product's technical documentation.
Where and how to install the tank
The pressure tank should be placed on a solid, level floor or surface, in a thermally stable environment – basement, utility room, dry boiler room. Avoid:
- Environments with temperatures below 0 °C – water inside would freeze and damage the tank
- Environments with temperatures above 40 °C for a long time – the rubber vacuum ages faster
- Direct sunlight in the case of outdoor installation – UV radiation degrades the rubber and galvanized coating
- Humid environments without ventilation – accelerates corrosion of the outer shell
The tank is connected to the common pipe after the pump and before the pressure switch – or more precisely: pump → T-piece → (one branch to the pressure tank, the other to the household network) → pressure switch. The pre-pressure of the air is adjusted using a valve nipple (similar to an automobile tire valve) on the tank's top before the first filling. A detailed installation procedure can be found in the article Installation of a pressure tank to a household water system step by step.
How much it all costs – approximate price ranges and what affects the price
The prices of pressure tanks range in the following approximate ranges (prices without VAT, for standard home use):
| Type / Capacity | Material | Approximate price | Typical use |
|---|---|---|---|
| 20–24 l | steel / galvanized | 25–55 € | Cottage, garden, 1 person |
| 50–80 l | galvanized with vacuum | 80–140 € | House, 2–3 people |
| 90 l | stainless steel | 180–270 € | House with drinking water, acidic water |
| 200 l | galvanized | 220–350 € | Larger house, 4–6 people |
| 300 l | stainless steel / galvanized | 400–750 € | Large house, farm, guesthouse |
The price is mainly influenced by: tank material (stainless steel is more expensive), volume, maximum working pressure, quality of the bladder, and certifications for potable water. Cheap tanks without potable water certification will save you money at the time of purchase, but they may cause problems during hygiene inspections or system maintenance.
Practical scenarios from everyday customer practice
Scenario 1 – Cabin with a garden: The customer has a new garden pump station with a power of 0.6 kW, a well with sufficient water, and 3 irrigation zones. They need something compact that stops cycling, but it doesn't have to be a large tank. Solution: Aqua OLA 24 l horizontal, pre-pressure 1.5 bar, switch set to 1.8/3.5 bar. After 2 years of operation without problems – the pump runs longer cycles and the customer is satisfied.
Scenario 2 – Older house with corrosion: The customer had a 15-year-old galvanized tank without a bladder. The well water had a pH of 6.2 – acidic. Result: strong internal corrosion, brown water when turned on. Solution: replacement with a stainless steel tank CH 90 L with a membrane bladder, certified for potable water. Prior to that, water analysis and installation of a neutralizing filter. After replacement, the water was clear even in the morning when the tap was first opened.
Scenario 3 – New family construction: A house with 2 bathrooms, a kitchen, a dishwasher, a washing machine, and an outdoor irrigation system, for 4 people. A submersible pump of 1.5 kW was designed, well depth 40 m. Tank volume based on calculation: minimum 80 l, selected HVP 200 L galvanized vertical. Result: the pump starts on average 2–3 times per hour even with intensive use, stable pressure in the whole house 3.2–4.0 bar.
Scenario 4 – Guesthouse with 12 rooms: The owner had a private well and one month after the season opened, problems started – pressure dropped during the morning peak and the pump ran continuously. The original 50 l tank was undersized. Solution: adding a second HVP 300 L tank in parallel to the existing setup. Interesting: sometimes it is cheaper to add a second tank than to replace the entire pump. After expansion, the tank handled the morning rush without problems.
Most common mistakes when choosing a pressure tank
- Undersized volume: Buying a 24-liter tank for a four-bedroom house with intensive use. The pump cycles, lifespan decreases.
- Ignoring water quality: Installation of a galvanized tank without a bladder in an area with acidic water – corrosion will appear within 5 years.
- Incorrect pre-pressure setting: Pre-pressure set too low or too high – the usable water volume in the tank is dramatically reduced or the bladder is damaged.
- Purchasing a cheap tank without potable water certification: Hygienic risk and problems during inspections.
- Installation without a check valve: Water flows back into the well between cycles – increased turbidity and pump damage.
- Forgetting the pressure gauge: Without a pressure gauge, you don't know what pressure range the system is operating in, and you cannot diagnose problems.
Maintenance and lifespan of a pressure tank
A pressure tank is not a "set it and forget it" device. At least once a year, you should check the pre-pressure of the air (disconnect the pump and release the water pressure from the tank first), the condition of the anti-corrosion coating on the outer shell, and the sealing of the connection. Every 3–5 years, consider replacing the membrane bladder, especially if you notice a drop in pre-pressure without an obvious cause – this indicates that the rubber is becoming porous. A detailed service protocol is described in the article Maintenance and service of pressure tanks – what and when to check.
The typical lifespan of a tank made of quality steel or stainless steel is 15–30 years, during which the bladder will be replaced 1–3 times. Therefore, an investment in a good tank is really a long-term one.
Frequently asked questions (FAQ)
Can I connect a larger pressure tank to an existing pump than the manufacturer recommends?
Yes, a larger tank than the minimum recommended by the pump manufacturer is always fine – the pump will start less often and will last longer. A problem occurs only the other way around: a too small tank for a powerful pump. No pump will be damaged by a larger tank. The only practical limitations are space and price.
Why does water bubble out of the tap immediately after turning it on?
This is a classic sign of a tank without a bladder, where air is in direct contact with water. Air dissolves in the water and is released in the form of bubbles when pressure drops. The solution is either regular air topping up and checking the pre-pressure, or replacing the tank with one that has a membrane bladder, where air and water are separated.
Do I have to buy a tank of the same brand as the pump?
No. A pressure tank is independent of the pump brand – it is connected with a standard threaded connection (usually 1" or 6/4" thread). It is important that the maximum working pressure of the tank matches or exceeds the pump's cut-off pressure, and that the connecting dimensions are compatible. Therefore, always check the diameter of the connection on the T-piece.
The tank has lost its pre-pressure within a few months – what is wrong?
If a galvanized tank without a bladder loses pre-pressure, air is dissolving into the water – this is normal behavior for this type of tank, and you must regularly top it up. If your tank has a bladder and is losing pre-pressure, the bladder is likely porous or the rubber has cracked. Check the air valve (it may be leaking), and if it is in good condition, remove the tank and replace the bladder. Problems with pre-pressure are addressed in more detail in the article Common pressure tank faults and how to fix them.
Is it more cost-effective to buy one large tank or two smaller ones?
Technically, the result is the same if the total volume is the same – two 100-liter tanks function the same as one 200-liter tank. In practice, one large tank is cheaper to buy, but two smaller ones can be more convenient in limited space conditions, during step-by-step system construction, or if you want to have a backup in case one fails (for example, during bladder replacement).
Can I use a pressure tank for hot water (solar system)?
No, standard pressure tanks for home water systems are designed for cold water at temperatures up to 30–40 °C. For circulation and expansion systems with warm or hot water (central heating, solar), special expansion tanks with a different type of membrane resistant to high temperatures are used. Using a standard pressure tank would lead to rapid degradation of the bladder and tank failure.
Conclusion – how to choose the right one then?
Selecting a pressure tank is not rocket science if you know a few key facts about your situation. Let's summarize it into a simple decision-making framework:
- First, determine water quality – pH, hardness, iron content. Acidic or aggressive water requires a stainless steel tank.
- Calculate the required volume – based on the number of people, pump power, and desired intervals between starts.
- Decide on a bladder – always yes for potable water, with certification for contact with potable water.
- Choose orientation based on space – usually vertical, horizontal only in height limitations.
- Don't buy on the edge – better to choose a volume one step higher, extra capacity will only extend the pump's lifespan.
On the page pressure tanks, you will find the entire range from compact horizontal tanks through medium galvanized variants to large stainless steel solutions for demanding operations. If you are unsure, other articles are also available in the Knowledge Center – for example, Common questions about pressure tanks for home water systems or What volume of pressure tank do I need for my house – where you will find specific calculation tables and other practical information.
Do you have a question about this topic?
Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.