Chapter 2. Utilities and Heating. Boiler piping in a private house: schemes, components and cost.

The boiler alone is just a heat source. To run safely and efficiently it needs a full set of components between itself and the heating system — the boiler piping kit. Without proper piping, even an expensive boiler short-cycles, overheats and fails early.

Circulation pump

The pump is the heart of the heating system. Wet-rotor — in-fluid rotor, quiet, maintenance-free, up to 300 m² (Grundfos UPS, Wilo Star-RS). Dry-rotor — higher efficiency but noisy, for large systems.

For a 100 m² house: head 4–6 m, flow 1.5–2.5 m³/h. Modern models (Grundfos Alpha3, Wilo Yonos PICO) modulate automatically, saving up to 50% electricity. Install on the return before the boiler — cooler fluid extends pump life.

Three-way mixing valve

Mixes cooled return into hot boiler supply. The boiler delivers 60–80 °C but underfloor heating needs 35–45 °C. Without the valve, floor pipes overheat and screed breaks down. Thermal head for simple systems, servo-driven for smart-home setups.

Expansion tank

Water expands when heated. Without somewhere to go, pressure spikes and the safety valve opens. A membrane tank accommodates the expansion — 10% of total coolant volume. For a 100 m² house (60–80 L coolant) — a 10–12 L tank, mounted on the return before the pump, air chamber up.

Safety group

Mandatory in closed systems. Three devices on one manifold: pressure gauge (norm 1.0–2.0 bar), auto air vent, safety valve (opens at 3 bar). Installed on the supply line at the boiler outlet. Never place a shut-off valve between the boiler and the safety group.

Shut-off fittings

• Ball valves at every component — isolate for service without draining

• Strainers before pump and boiler — catch scale and rust, clean once a year

Hydraulic separator

Needed with multiple loops of different flow rates (radiators, underfloor, indirect cylinder). Without it, loops steal flow from each other. A vertical vessel connects boiler supply/return and all consumer loops; flow slows, pressure equalises, each loop gets exactly what it needs.

When required:

• Two or more loops with their own pumps

• Boiler power above 50 kW

• Flow difference between loops more than 2×

For 80–120 m² houses with one radiator loop and one underfloor loop, a separator is not required — a manifold with a thermal valve is enough.

Typical layout

1. Boiler supply → safety group → manifold / radiators

2. Return → strainer → circulation pump → expansion tank (branch) → boiler

3. Ball valves at every component

Wall-hung boilers with built-in pump and tank simplify the kit: safety group, filter and valves remain external.

Common mistakes

• No strainer before the boiler — exchanger clogs in 1–2 seasons, 15 000–25 000 ₽ repair

• Expansion tank on supply instead of return — faster membrane wear

• Shut-off valve between boiler and safety group — dangerous

• Undersized expansion tank — safety valve keeps opening

• No drain valve — servicing becomes a nightmare

Cost (2026)

StroyInvest24 designs and installs boiler rooms across the Leningrad Region to full safety standards, with a workmanship warranty.

See also

• Choosing a gas boiler

• Turnkey heating system

• Flue for a gas boiler

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