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Heating · Hydronic RepairRadiant Floor Heating Repair
Radiant floor heating repair starts at the manifold, not at the floor: one cold loop is nearly always an actuator, an air lock, a closed balancing valve or a dead thermostat, and a whole floor running cool is usually the mixing valve or the circulator. A diagnostic visit is $90–$150, and most of these faults are fixed for $150–$800 without lifting a tile.
Start with what is cold. If one room is cold and the others are warm, the heat source is fine and the fault sits at that loop's branch on the manifold. Each loop has a small thermal actuator that opens when its thermostat calls, and a failed one stays shut while its neighbours open. The other suspects are an air lock in that loop, a balancing valve or flow meter that got turned down, and a thermostat or zone module that never sends the call.
If the whole floor is lukewarm, look upstream. A thermostatic mixing valve blends boiler water down to the 35–45°C a floor wants, and when its element sticks it either starves the floor or sends water hot enough to damage the flooring. A seized circulator leaves the supply pipe hot at the boiler and cold a metre along. We measure supply and return temperatures at the manifold before replacing anything, and faults at the heat source fall under boiler repair.
A suspected leak is proven before any floor is opened. Each loop is isolated at the manifold and pressure-tested alone, so a loop that will not hold is identified by number. A thermal camera then shows the tubing pattern through the finished floor and the spot where the heat stops or blooms. Tubing buried in a slab rarely fails without help: the leaks we find are at manifold fittings, or where a flooring nail, a door-stop screw or a wall anchor went through a loop.
Know which kind of floor heat you have before you call. A hydronic system has a manifold with a row of tubes, and it is boiler, pump and valve work. An electric mat under bathroom tile has no manifold, only a thermostat with a floor sensor. For new loops or an added zone, see radiant floor heating installation; for a fault on an existing system, book a diagnostic visit.
Call for radiant floor repair when
- One room's floor is cold while the next loop on the same manifold is warm
- The whole floor is tepid and the boiler never seems to shut off
- A circulator is humming, too hot to touch, or silent while the thermostat is calling
- The pressure gauge keeps falling and you are topping the system up by hand
- One patch of floor is far hotter than the rest, or damp shows at a baseboard or on the ceiling below
How it works
Supply and return temperatures, the flow meter on each loop, and every actuator checked against its thermostat call. Ten minutes at the manifold usually tells us whether the fault is one loop or the whole system.
The circulator, the mixing valve outlet temperature and the system pressure are measured. If pressure is dropping, loops are isolated and tested one by one and the floor is scanned with a thermal camera. You get the finding and the price in writing.
The part is replaced, each loop is purged of air individually, the pressure is reset to about 12–15 psi cold and the flows are rebalanced. Floor temperatures are checked again once the slab has had time to respond.
Common questions
Do you have to break up the floor to fix a leaking loop?
Only at the proven spot, and only when the leak is in the floor at all; many turn out to be at the manifold. When a loop has been pierced, a small section of flooring or slab is opened and the tubing spliced with an approved coupling. If the damage sits under cabinetry or stone, abandoning that one loop and rebalancing the rest is sometimes the better answer.
Why is the floor cold at the start of the heating season?
Parts that sat still all summer are the usual cause. Actuators stick shut, a circulator that has not turned since April seizes, and air collects at the manifold. Running each zone for an hour in late September shows you the problem while it is still mild. One dead zone and one live one is covered in why a heating zone stops working.
How long before the floor feels warm again after a repair?
A concrete slab takes hours, not minutes, and a slab that has gone fully cold can need most of a day to come back to temperature. Tubing stapled under a wood subfloor recovers faster. Judge the repair by the supply and return temperatures at the manifold that day and by the floor the next morning, not by your feet an hour later.
Why is there black sludge in my radiant system?
It is usually iron oxide. Tubing without an oxygen barrier lets oxygen pass through its wall into the water, and that corrodes cast-iron pumps and steel fittings from the inside. The sludge then blocks flow meters, actuators and mixing valves. The fix is a hydronic system flush with inhibitor, and on some systems separating the tubing from the boiler with a heat exchanger.
Can you repair electric in-floor heating?
Our work is hydronic: boilers, pumps, valves, manifolds and tubing. An electric mat or cable system is an electrical circuit, and a dead thermostat, a failed floor sensor or a damaged cable belongs with an electrician working under ESA rules. If you are not sure which system is under the tile, a photo of the wall control is usually enough for us to tell you.