A hydroaccumulator is a sealed tank with an internal diaphragm that stores water under pressure. In Israel, it's installed in private homes (villas) with a well/borehole pump, in apartments with a dedicated booster pump, and in systems with recurring water hammer. A properly sized and installed pressure tank means a quieter pump, stable pressure, and protection from unnecessary wear.
Why a hydroaccumulator is needed
Three main jobs:
- Fewer pump starts. Without a tank, the pump kicks in every time you open a tap. With a tank — it fills the tank under pressure, then feeds fixtures from the tank. The pump cycles 3–5 times an hour instead of 30–50. Service life goes up 5–10×.
- Pressure stabilization. You open a tap, pressure drops — the tank compensates from its reserve while the pump spins up. The stream doesn't stutter.
- Water-hammer protection. The diaphragm absorbs sharp pressure spikes — pipes and fixtures last longer.
Where it's installed
Private home with a well/borehole pump
Mandatory. Without a tank, the pump "burns out" in 2–3 years from endless cycling. With a 50–100 L tank, it runs for 10–15 years.
Apartment with a booster pump
In old apartment buildings, top floors suffer from weak pressure — a small booster pump is installed (with a 20–50 L tank). The tank is mandatory.
Home with a well as backup supply
When switching between "mains / well," the tank smooths the transitions.
Yard irrigation system
With a dedicated pump — a small 20–50 L tank for drip irrigation.
Before a boiler with a solenoid valve
Sometimes a 5–10 L expansion tank is fitted to compensate thermal expansion — functionally similar, but not quite a hydroaccumulator.
Sizing the tank
Tank volume is selected based on pump output and consumption profile:
- Apartment, 1–2 draw-off points — 20–24 L is enough.
- 3–4 room home on a well — 50–80 L standard.
- Large home with 2–3 bathrooms — 100–150 L.
- Home + garden + irrigation — 150–200 L, sometimes several tanks in parallel.
Rule of thumb: tank volume = pump output per minute × 3–5. A pump delivering 40 L/min → a 120–200 L tank.
Orientation — horizontal or vertical
- Vertical — takes less space, sits in a corner. Standard for smaller tanks (up to 50 L).
- Horizontal — more stable stance, pump mounts on top. For tanks 80+ L.
Connection diagram
Standard diagram for a private home:
- Pump — draws from the well/borehole.
- Check valve — right after the pump, so water doesn't drain back into the well.
- Five-way fitting — where the pump, tank, gauge, pressure switch, and line to fixtures meet.
- Hydroaccumulator — on one port of the fitting.
- Pressure switch — starts/stops the pump on pressure drop/rise.
- Pressure gauge — visual check.
- Line to fixtures — on into the home distribution.
Air pressure in the diaphragm
The air side of the diaphragm is pre-charged 0.2–0.3 bar below the pump cut-in pressure. For example, pump turns on at 2 bar, off at 3 bar — diaphragm at 1.8 bar. Incorrect pre-charge is the main cause of premature diaphragm wear.
How the installation goes
- Choose the location. Flat surface, service access, a power outlet nearby (for the pump). For heavy tanks (50+ kg) — check floor load capacity.
- Check diaphragm pressure before connection (with a gauge on the valve). Top up or bleed as needed.
- Assemble the manifold — five-way fitting, pressure switch, gauge, tank.
- Connect to the pump and to the mains — on threaded joints with sealing.
- Tune the pressure switch — upper (cut-out) and lower (cut-in) limits. Usually 1.5/3 bar or 2/4 bar.
- Power up and test. Open a tap, watch the pump start/stop behavior.
Pricing in Israel
- 24 L hydroaccumulator (small apartment) — 250–450 ILS hardware + 300–500 ILS labor
- 50 L hydroaccumulator — 400–700 ILS + 400–700 ILS labor
- 80–100 L hydroaccumulator — 600–1,200 ILS + 500–900 ILS labor
- 150–200 L — 1,000–2,000 ILS + 700–1,400 ILS
- Full "pump + tank + switch + automation" installation from scratch — 2,500–6,000 ILS labor + hardware
- Replacing the diaphragm in an old tank — 150–400 ILS labor + 80–250 ILS diaphragm (if the part is available)
- Pre-charging the diaphragm (scheduled or on pressure loss) — 150–250 ILS
Popular models in Israel
- Aquasystem (Italy) — premium, wide range, 10+ years.
- Varem (Italy) — reliable mid-range.
- Reflex (Germany) — quality, availability.
- Zilmet (Italy) — good price/quality ratio.
- Jeelex, Vikhr — ex-USSR brands, less common.
- Chinese no-name — lasts 2–4 years, half the price. For temporary solutions.
Common issues and maintenance
- Pump cycles frequently. Diaphragm pressure has dropped — pre-charge via the valve with a car tire pump.
- "Wet" charge valve. The diaphragm is ruptured — water has entered the air side. Diaphragm or whole-tank replacement.
- Noise from the tank. Limescale has built up inside — heavy fouling damages the diaphragm. Prevention — inlet filter.
- Tank "feels full" but is empty. Air trap or ruptured diaphragm — water stays stuck.
Maintenance: check diaphragm pressure annually, replace the diaphragm every 3–5 years. Tank life — 10–15 years with proper care.
Frequently asked
Is a hydroaccumulator mandatory in a private home?
With a well/borehole pump — practically yes. Without a tank, the pump runs to failure and burns out in 2–3 years. A tank at 500–1,500 ILS vs a pump at 1,500–4,000 ILS — pays back quickly. Going without a tank is acceptable only with variable-frequency pumps (more expensive).
My pressure tank is 8 years old. Should I replace it preventively?
If it runs stably, the diaphragm holds pressure, no moisture at the valve — leave it alone. But check pressure yearly and listen to the pump. The first warning sign is increased cycling frequency. Then inspect the diaphragm.
Can I use a heating-system expansion tank for water?
No. Heating tanks have a diaphragm made of material not intended for potable water. Long-term contact — water starts to "smell" of rubber or absorbs additives. For potable water use only purpose-built tanks with food-grade diaphragms (FDA marking / אישור משרד הבריאות).
Where do I put the tank if there's no utility room?
Vertical 24–50 L — in a kitchen cabinet under the sink, in a hall closet, in a plumbing cabinet niche. Key requirement — access to the charge valve and fittings. For larger tanks (80+ L) — a separate room or a technical corner on the property.