Loadshedding Is Killing Hot Water Recirculation Pumps. Here's How to Protect Yours.

Larger South African homes — typically 4+ bathrooms, or any home with a long pipe run from geyser to the furthest tap — often have a hot water recirculation pump on a ring main. It keeps hot water at the tap within 5–10 seconds instead of 60–90 seconds, saving water and frustration. Since 2022, these pumps have been failing at roughly three times the historical rate. The cause is almost entirely loadshedding.

How the damage happens

Most SA installations use small wet-rotor circulation pumps — Grundfos UP/Comfort, Wilo Star-Z, DAB Evosta. They run continuously or on a timer, drawing 25–95 W.

Loadshedding hurts them in three ways:

1. Dry-start damage — when the power cuts mid-cycle and the pipe partially drains back through a leaky non-return valve, the pump can restart against an air pocket. Wet-rotor pumps need water for bearing lubrication and cooling. 10 seconds dry-running is enough to score the ceramic bearing.
2. Voltage spikes on restoration — Eskom and many municipalities deliver a noticeable spike when supply is restored. Pump electronics (especially newer ECM-driven models) are sensitive above 250 V.
3. Stall + thermal trip cycling — a pump trying to start against system pressure shifts during a loadshedding return can stall, trip on overload, cool, restart, stall again. Five cycles of this and the windings are cooked.

Symptoms of a dying pump

• Hot water takes longer to arrive than it used to
• Audible grinding or rattling from the cupboard housing the pump
• Pump body unusually hot to touch (>70°C) when it should be 40–50°C
• Frequent thermal trips that reset after the unit cools
• Visible green corrosion at the cable gland (water ingress after seal failure)

Protection that actually works

1. Surge protection device rated for the pump's supply — a R280 DIN-rail SPD on the geyser circuit prevents 90% of voltage-spike kills.
2. 30-second restart delay relay (R450) — wired in series with the pump's live. After power restoration, it waits 30 seconds before allowing the pump to start, letting the system settle and avoiding the immediate dry-start surge.
3. Loadshedding-aware controller — Grundfos Alpha 2 and Wilo Stratus have AutoAdapt functions that ramp speed instead of slamming start. Worth the R2 500 upcharge on a replacement.
4. Check valve service — replace the spring-loaded non-return on the cold feed and the return leg every 5 years. A failed NRV is what causes the dry-back in the first place.

What about a UPS on the pump?

A small UPS keeping the pump running through a 2-hour stage 6 cycle is overkill — the pump can safely shut off and restart if the system is healthy. The damage is restart-related, not run-related. Spend the money on the SPD and delay relay instead.

When to replace, not repair

Wet-rotor pumps are sealed units. Bearing failures are not field-repairable. If the pump is more than 7 years old or has had two thermal trip events in a month, replace it — and add the SPD and delay relay to the new install. Total replacement plus protection: R3 800–R6 500 for typical residential ring mains.

A note on continuous-run pumps

Many installs run the pump 24/7. With current electricity prices, switching to a timer (06:00–09:00 and 17:00–22:00) saves around R110/month and also reduces the cumulative hours of loadshedding-related stress. The hot water ring loses maybe 1°C per off hour — barely noticeable at the tap.