Hydroaccumulator tank: how it works, purpose, calculation and selection, installation, difference from storage, expansion tanks

Knowing the ins and outs of insulation and heating systems is essential for maintaining a warm and comfortable home. One crucial element that is frequently disregarded is the hydroaccumulator tank. However, what is it precisely and why is it relevant? Now let’s get started.

In many heating systems, especially those that use water as a heat transfer medium, a hydroaccumulator tank is an essential component. Its main function is to hold pressurized water, which keeps the system’s flow constant and steady. Consider it as a buffer that evens out pressure variations while preserving peak efficiency.

How then does it operate? In actuality, it’s fairly straightforward. Usually, the heating system and main water supply are connected to the tank. The hydroaccumulator tank takes up the extra volume that the heated water expands to, preventing pressure buildup and possible system damage.

There are a few things to take into account when choosing the ideal hydroaccumulator tank for your house. Size is the most important factor. Finding the amount of water your system needs and factoring in demand variations are essential steps in choosing the right size.

Although installing a hydroaccumulator tank is not too difficult, it is imperative to adhere to local building codes and manufacturer instructions. The tank is usually placed close to the heat source or boiler to allow for simple maintenance and inspection.

It’s crucial to understand how a hydroaccumulator tank differs from other kinds of tanks, like storage and expansion tanks, that are frequently utilized in heating systems. As expansion tanks manage thermal expansion and storage tanks merely hold water for later use, the hydroaccumulator tank plays a special function in preserving system performance and pressure.

Why do you need a cold water accumulator tank

Hydroaccumulators, or HAs, are used in water supply systems that include boilers, storage tanks, pumps, and wells for residential buildings.

• head equalization, protection against hydrostroke;
• small reserve in case of water supply failure, electricity for pumps;
• optimal conditions for:

• pumping station (NS), so that it does not turn on every time the taps are opened, which quickly reduces its service life;
• of the whole equipment – the pump creates water shocks, shocks, increase/decrease of loads. If the water is supplied through the GA, the flow is stable.

The principle of operation of a hydro storage tank

The hydroaccumulating tank’s design:

• rounded body – cold water accumulator tanks are made of stainless steel:

• horizontal – less ergonomic, but convenient, surface pump is attached to the body;
• vertical installation – to save space, often used for submersible pumps. With an additional bleed valve at the top;

• legs, stand, horizontal models have a mount for a compact NS on top;
• spigot with flange (steel, plastic) for pumping in/out the liquid;

• radial diaphragm (less frequent, risk of corrosion is higher);
• Balloon (pear) – more common, reliable, easy to replace;

Distinction between the various accumulator tank construction variations:

Vertical	Horizontal placement
Air in the upper segment, so there is an additional nipple for a bleed-off device.	Bleeding is more difficult. A nipple, ball valve, drain will be required. For small hydro accumulators (up to 100 liters) it is simpler: disconnect the power, open the faucet, wait for it to empty, close the faucet, reconnect and refill.

Horizontal GA and pump are frequently sold with a pressure gauge and relay (automatic pumping unit with hydroaccumulator tank) or connected in a modular version.

How the hydroaccumulator membrane tank works:

1. The tank is filled with cold water.
2. Diaphragm (balloon) made of rubber expands, air compresses, increasing pressure.
3. Once the set mark is reached, a relay switches off the pump and the supply is stopped.
4. Then, the GA works: the pear is compressed, it pushes the liquid out. But the device itself does not pressurize or pump, the HC does all of that. As the pressure is consumed, it gradually decreases to a preset minimum, the relay reacts, closes the contacts that turn on the pump – the cycle repeats.

What should be the pressure in the accumulator?

At the factory, the manufacturer sets the initial internal pressure of the accumulator tank between 1.5 and 2 atm. It is adjustable by the user.

In order to provide a small reserve until the next activation, the air pressure in the hydraulic accumulator’s empty tank should be between 10 and 12 percent lower than the minimum required for pump start. It will take 3 – 0.3 = 2.7 bar to activate the HC at 3 bar. Alternatively, the factory setting may be left at 1.5 volts, and a 2 to 2.5 volt switch is set; this adds the designated percentage to the initial, pre-set value.

The pressure inside the product does not directly correlate with its volume; instead, the membrane’s properties have a greater impact on the frame. The manufacturer typically allows for 24 to 150 liters: 200–500 liters: 2 atm, 1.5 atm.

Car and bicycle pumps reduce the number of atmospheres by pumping air into the hydroaccumulator tank through the spool. When the tank is empty, the reading is verified using a standard manometer.

Maintain a specific air pressure balance in the tank; for a product with 1.5 atm, for example:

• at a small consumption of a single-storey building, if there is a need for a larger reserve, it is allowed to reduce, but only to 1 atm. A low indicator is better, the load is reduced, the wear and tear of the pipes, but the pressure will also weaken;
• Excessive reduction is undesirable: the pear stretches, comes into contact with metal walls, which shortens its service life;
• excessive pressure (above 1.5 – 2 or 3 atm.) is also harmful: the rubber diaphragm is compressed more, the usable volume is reduced, and there will be an increased load.

Technically speaking, household product housing should be able to withstand pressures of up to 10 bar, but not any lower than the maximum pressure for which the pipeline is intended.

Hydroaccumulator and expansion tank – what is the difference?

The differences in function, components, and specific areas of operation between a hydraulic accumulator and an expansion tank. Although their designs are comparable, they are distinct devices, so you cannot swap one for the other.

• water supply;
• equalizes differentials, eliminates water hammer;
• there is a reserve function.

• heating;
• compensates for the expansion of the coolant, which puts an excessive load on the pipes.

• in the inner rubber cylinder water that does not contact with the walls of the housing (except for products with radial diaphragms);
• liquid is pumped into the vessel cylinder and expelled as it is consumed. HC is switched off, resource is saved, energy is saved (it works only to fill the vessel) plus head stabilization.

• in the diaphragm chamber compressed air, in the casing the heat transfer medium in contact with the walls;
• cycle:

• Expanded fluid increases, flows in, the load on the pipes is reduced;
• after cooling, the heat transfer medium is reduced, pushed back out by the straightening diaphragm.

Additionally, inertial accumulating vessels (often gray) with boilers, heat pumps, refrigeration, cooling, and air conditioning equipment must be distinguished from the GA. These vessels’ functions include removing excess heat, increasing inertia, and balancing heating.

Hydroaccumulator or storage tank – what is better

This is a basic reserve tank, accumulator. Which device—or two at once—is necessary is the more important question.

For instance, selecting options for a well. Install an accumulator, automation, and a submersible pump if the debit is low and the GA is positive. A small GA (24 to 30 liters) is sufficient if the blower is strong and there is no suction after 20 minutes. Place the accumulator if the debit is negative and the site requires a high flow rate, like for irrigation; nevertheless, a hydroaccumulator should still be added.

GA	Storage tank
Under pressure, accumulates hydraulic energy, returns it under specified conditions.	No accumulation of hydraulic force. The liquid is supplied by gravity (Rozhnovsky tower) or by means of electromechanical devices.
Basic water supply of private houses with external NS with positive flow rate for all needs.	In case of low-power equipment, e.g. for wells with submersible pumps. Where you do not particularly need protection from hydrostroke, stabilization, and only need a reserve before the resumption of the water column.
Required wherever good, stable pressure is needed.	If the flow rate is low and the instantaneous flow rate is high. So that the pump does not switch off when idling.
	GA have a smaller volume (average maximum 100 – 200 liters), so where periodically turn off the supply, put a storage tank for 1000 – 1500 liters

It is pertinent to inquire as to the most effective means of guaranteeing the liquid supply. The hydroaccumulating membrane tank’s increased volume for cold water supply systems has no appreciable impact on how well it functions. The primary goal is to preserve equilibrium and composure rather than to amass wealth. Purchasing an enlarged GA is pointless if a reserve is required; instead, the circuit should be designed with an accumulator. However, if the user wishes to integrate all features into a single device, this is possible.

However, a large GA makes sense if there are frequent power outages or if NS cycle counts must be kept to a minimum. Additionally, keep in mind that the water in the tank makes up roughly one-third of the GA. The pear is always made to hold a smaller volume of liquid—80 to 100 liters in a 150-liter tank, for instance.

A small GA plus two storage tanks, one for irrigation (at a height for self-flow) and the other for household needs, would be the perfect combination for a private home. A feasible water supply system variant that uses a membrane tank hydroaccumulator: a submersible blower from the well fills the storage tank, and a GA feeds the resource surface from the house system.

• not for a large reserve, such function is available, but it is secondary;
• the cost of accumulator tanks for cold water is higher, as well as spare parts;
• requires proper piping, calculation, adjustment;
• maintenance is more complicated.

• complex of functions: pressure equalization, reserve, reducing the load on the equipment;
• full-fledged temporary operation at system shutdown is not worse than if the NS was working;
• ready-made device with automation.

• complexity of automation;
• does not smooth out the pressure;
• water stagnates (the problem is solved by periodic skipping).

• unpretentiousness, maintenance is not complicated;
• large volumes (up to 2000 liters and more);
• cheapness of the product (often plastic, PVC, polyethylene), repair;
• it is possible to organize a gravity flow scheme or make automation with a pump.

Tightness and load-bearing capacity are crucial for GA, so carbon steel—which is safe for drinking water—rather than polymers or plastics are used for the housing materials. A unique polymer-epoxy paint is applied outside, and a polypropylene liner serves as a protective layer within.

Because there are no unique load requirements or tank material options, the accumulator is less expensive.

• PVC;
• cross-linked polyethylene high or low pressure;
• polypropylene;
• more expensive: stainless steel or plain steel, inside coated with lacquers, bioglass porcelain, enamel.

Calculation of the cold water accumulator tank

Calculate the necessary bar or atm using the following formula:

An example of a calculation would be to assume that Hmax = 7 m for a 2-story building.

7 + 7 / 10 = 1.4 atm is P.

Prior to choosing the product, a preliminary capacity calculation (volume) must be made using the following formula:

Adjustment factors for accumulator volume calculation:

Pump capacity, kW	0,55 – 1,50	2,20 – 3,00	4,00 – 5,50	7,50 – 9,00
Coefficient	0,25	0,375	0,625	0,875

An illustration of how to calculate the minimum tank volume needed is:

• Amax 115 l/min.;
• Pmin = 1.6 bar;
• Pmax = 3.7 bar;
• Pprec = 1.3 bar;
• HC capacity = 4 l/s (K = 0.675).

• 0,625 х 115 = 71,88;
• (3,7 +1) х (1,6 +1) = 12,22;
• (3,7 – 1,6) х (1,3 +1) = 4,83;
• 71.88 x (12.22 / 4.83) = 181.86 liters.

Using the fixed data table, the volume is chosen in accordance with the initial number of Bar in the hydraulic accumulator tank and the pump start values.

Table showing the hydraulic accumulators’ filling capacity

Volume of water stored (l)

In the realm of home heating and insulation, understanding the role of a hydroaccumulator tank is crucial. This specialized tank serves multiple functions, primarily as a storage vessel for water in a heating system. Its key purpose lies in maintaining consistent water pressure, ensuring efficient operation of heating systems such as boilers or solar panels. Unlike traditional storage tanks, hydroaccumulators use compressed air to store water, allowing for better regulation of pressure fluctuations and reducing strain on the heating system. Calculating and selecting the right size hydroaccumulator is essential to match the demands of the heating system and household usage. Installation involves connecting the tank to the heating system"s water circuit, typically near the boiler or heat source. It"s important to note the distinction between hydroaccumulators and expansion tanks, as the latter primarily deal with thermal expansion in closed-loop heating systems, while hydroaccumulators focus on pressure regulation and water storage. Understanding how hydroaccumulator tanks work and their role in a heating system is fundamental for homeowners looking to optimize their home"s energy efficiency and heating performance.

What brand of accumulator tank to choose

Popular brands available:

• JILEX is an inexpensive brand with quality issues. Often requires artisanal improvements, in particular sealing (there are uneven enamel in the places of pressing), tightening the bolts of the flange, which is rotten. Pros: low price;
• Aquasystem – produced in Russia from Italian components. Large assortment, acceptable quality, average price. Often the diaphragm is made of EPDM (ethylene propylene rubber), this is the standard, but there are better materials (butyl rubber);
• WESTER is analog of Aquasystem, sometimes a little cheaper. Vester has similar reviews;
• Zilmet, Varem – proved to be good, high price range, butyl membrane, which is much better. Varem has a lower price;
• Reflex – is positioned as a German brand, but hydroaccumulators are assembled in Russia. Reflex has a high price, not bad quality;
• Belamos – positioned as a cheap brand, but in this segment it is better than similar ones;
• WWQ – solid middle ground, despite being made in China, reasonably priced;
• Caliber – there are comments, but in general the reviews are not bad, which together with the low price makes the purchase practical;
• Unipump – mid-price segment. Unipump product reviews vary;
• Cimm – reliable products in the medium price segment.

• The hydraulic accumulator must have hygienic certificates, the purpose is for drinking water;
• Butyl rubber membranes are better than EPDM;
• preferably spare diaphragms, flanges;
• quality flange – made of galvanized or stainless steel thicker than 1 mm. However, plastic elements are also put on quality products, as they do not corrode, but there is a risk of cracking;
• the diameter of the spigot should be matched as closely as possible to the pipes of the system, but adapters are also used.

Scheme of piping of the accumulation tank

• Pump;
• hydro accumulator;
• automatics: pressure switch (electric regulator of the cold water level);
• check valve;
• Filter (not always, but desirable).

For connecting to common pipe diameters, a 5-wire connection is typically utilized. Although it will require more work, fittings and pipe sections can be utilized.

Connect to the leads:

• 1" – for screwing onto the vessel;
• 1/4" – for the relay and manometer;
• the other inch diameters are for the HC pipe and connection to the consumers.

Having a submersible pump connected:

Plan utilizing a boiler:

Simplified representation of the options:

It is easier to install surface apparatuses when you use a flexible hose wrapped in a metal wrapping with inch connections. The standard scheme is followed when connecting the submersible pump to the GA, taking the power supply and location into consideration. The hydroaccumulator is installed in the location where the pump’s pipes enter.

Suggestions for installation:

• several GAs of different capacities can be combined in parallel in a battery. The system will not have to be reconfigured – the relay monitors the parameters in the tank on which it is mounted. If one GA is damaged, the others will work. There is a financial benefit: 2 hydro accumulators of 50 liters are cheaper than one for 100 liters;
• location of the tank – a room with temperature from +5° C so that the water does not freeze and does not rupture the equipment: basements, first floors, first floors, technical rooms, utility rooms. Preferably with low humidity;
• standardly hydroaccumulator is mounted near the pump, if it is surface, horizontal models have mountings for it on its body. The height of placement (including below the water intake point) does not matter;
• the diameter of the supply line should not be smaller than the spigots on the body. Connection can be done with flexible hoses. Immediately after purchase check the pressure gauge, usually according to TD should be 1, 5 atm., minor deviations are possible due to long-term storage.

To prevent air locks, it’s crucial to install the tank in a location where there isn’t even the smallest misalignment (verify with a level). Rubber gaskets can be used to reduce vibration.

Hydroaccumulator Tank	Works by storing water under pressure, aiding consistent water flow.
Purpose	Ensures steady water pressure in the house, reducing reliance on pumps.
Calculation and Selection	Determined by household water demand and pressure requirements.
Installation	Installed near the water source with proper support and connection to the plumbing system.
Difference from Storage Tanks	Hydroaccumulators maintain pressure, while storage tanks only store water.
Expansion Tanks	Manage pressure fluctuations in closed-loop heating systems, unlike hydroaccumulators.

For your home’s comfort and energy efficiency, it is imperative that you make the appropriate insulation and heating system investments. The hydroaccumulator tank is one such part that is very important. This tank is essential for controlling the water pressure in your heating system, which guarantees steady flow and best efficiency.

Homes hoping to improve their heating systems must comprehend how a hydroaccumulator tank operates. In contrast to conventional storage tanks, which are only meant to hold water, hydroaccumulator tanks use compressed air to keep pressure levels stable. This implies that water is forced out of the system by air pressure when it is drawn, guaranteeing a constant flow free from variations.

There are a few things to take into account when choosing the best hydroaccumulator tank for your house. The secret is to figure out the right size based on how much water your home uses and how much your heating system can handle. Selecting a tank with sturdy construction and materials also guarantees longevity and low maintenance needs.

A hydroaccumulator tank installation calls for meticulous preparation and observance of safety regulations. For best results, the heating system must be positioned correctly, have enough support, and have secure connections. Securing the services of a qualified installer can guarantee a smooth integration of the tank into your current configuration.

It’s critical to distinguish between conventional storage or expansion tanks and hydroaccumulator tanks. Expansion tanks allow for thermal expansion within the system, whereas storage tanks only store water without controlling pressure. In contrast, the pressure levels in hydroaccumulator tanks are actively maintained, providing more accurate control and efficiency.

To sum up, adding a hydroaccumulator tank to your home heating system can have a lot of advantages, such as better efficiency, less energy usage, and steady water pressure. Through comprehension of its operation, appropriate model selection, and guaranteed installation, homeowners can maximize the comfort and efficiency of their heating systems.