A central water softener for an apartment block is installed on the building’s main water inlet, after the meter and usually before the booster pump. One system protects the shared plumbing, the pump, the roof tanks and every boiler, water heater, tap and appliance in all apartments. It is usually far more economical than each apartment buying its own unit.
Why a Central System?
- Protects common pipes, pumps and storage tanks, where scale is expensive to remove.
- One maintenance point instead of dozens of small units.
- Lower cost per apartment and lower salt use with a metered valve.
- Every resident gets soft water, including those who would not buy a unit themselves.
How to Size an Apartment Block Softener
Peak flow
Morning and evening peaks decide the valve and tank size. As a rough guide, a 10-unit block may need 2–3 m³/h, a 20–30-unit block 4–6 m³/h and larger blocks more; the exact figure depends on bathrooms per unit and pipe size.
Daily hardness load
Daily consumption multiplied by hardness gives the amount of hardness the resin must remove. This sets the resin volume and how often the unit regenerates. Too little resin means daily regenerations and high salt use.
Continuity
During regeneration a single-tank unit sends hard water through its bypass. If the building has hot water systems that must always receive soft water, choose a twin-tank (duplex) system where one tank is always in service.
Sizing Examples
| Building | Typical flow | Typical system |
|---|---|---|
| Up to 8 apartments | 1.5–2.5 m³/h | Single tank, 25–50 L resin, metered valve |
| 10–20 apartments | 2.5–4 m³/h | Single or twin tank, 50–100 L resin |
| 20–40 apartments | 4–6 m³/h | Twin tank, 100 L+ resin, 1″–1½” valve |
| Residential complex | Project-based | Several columns or industrial valve |
For example, our Runxin S-100 model with 100 litres of resin delivers 4 m³/h service flow. For hotels and offices see whole-building water softener.
Installation
- Install after the main meter, with a three-valve bypass so water continues during service.
- Add a sediment filter in front if the mains carries sand or rust (see limescale filter).
- A floor drain and a power socket are needed for regeneration.
- Leave space to fill the brine tank with salt bags.
Maintenance
Keep salt in the brine tank, check outlet hardness monthly with a test kit, and service the valve and injector once a year. With good resin and pre-filtration, resin lasts many years.
Price and Quote
The price depends on flow, resin volume, valve type and whether a twin-tank system is required. See water softener prices. Send us the number of apartments, water hardness, inlet pipe size and a photo of the plant room; we will size the system and quote in USD, including shipping to your country.
Frequently Asked Questions
Is one central softener enough for the whole building?
Yes, if it is sized for peak flow and daily hardness load. Larger buildings use twin-tank systems or several columns.
Where is it installed?
On the main inlet after the meter, usually before the booster pump, with a bypass, drain and power socket nearby.
Does the water pressure drop?
Not if the valve and tank are sized for the building’s peak flow. Undersized units cause pressure drops.