FAQ
TL;DR: For Galmet SGW(S) service, first test anode current—“above 1 mA is OK”—before unscrewing. If it reads 0.5 mA or less, plan a replacement or descaling. [Elektroda, dobroslaw, post #18054685]
Why it matters: DIY homeowners can avoid damaging insulation and make smarter repair calls on SGW(S) anodes and heaters.
Quick Facts
- Reported sizes: outer plastic cap ≈75 mm; inner hex ≈35 mm; anode/heater use a 5/4" wrench. [Elektroda, axl2, post #18051671]
- Tubular socket approach: a socket that fits inside, with an external hex for driving; approx. 30 mm may fit. [Elektroda, Rafikusa, post #18051877]
- Oversize cap tools exist in inches; 3-inch wrenches are available—verify fit on your cap. [Elektroda, bumble, post #18051804]
- Anode health guide: >1 mA OK; 0.5–1 mA monitor; <0.5 mA replace or scaled. [Elektroda, dobroslaw, post #18054685]
- Heater module orientation: mount with the cable downward for proper thermostat sensing. [Elektroda, Michelson, post #18055311]
What size are the SGW(S) anode/heater fittings and the outer plastic plug?
User measurements report a 75 mm outer plastic cap and a ~35 mm inner hex. The anode and heater take a 5/4" wrench. Always verify your unit before buying tools. [Elektroda, axl2, post #18051671]
Which tool works when the nut is recessed in insulation?
Use a tubular socket that fits into the cap and presents an external hex to turn. Approx. 30 mm often fits, depending on wall thickness and clearance. This lets you avoid cutting the foam. [Elektroda, Rafikusa, post #18051877]
Is a 3-inch wrench suitable for the outer cap?
Large cap wrenches are sold in inch sizes, and 3-inch options are available. Check the cap across-flats and confirm clearance before purchase. [Elektroda, bumble, post #18051804]
Can I build a DIY tool if I can’t source a huge socket?
Yes. One owner made a custom socket and drove it with a Swedish wrench to remove the cap. "Socket made of own design + Swedish wrench." This avoids destroying the insulation when large tools aren’t in stores. [Elektroda, axl2, post #18055432]
Can I use a bolt head as a makeshift inner-hex key?
An M24 bolt has a 36 mm hex head. You can use it as a 36 mm driver for the inner hex, if clearance allows. Check fit and avoid over-torquing plastic. [Elektroda, Michelson, post #18052302]
How do I measure if the magnesium anode still works without unscrewing?
Disconnect the anode’s cable and measure current between the anode and the tank body. >1 mA is OK; 0.5–1 mA warrants checking; <0.5 mA signals replacement or scale. "Above 1 mA is OK." This test saves unnecessary teardown. [Elektroda, dobroslaw, post #18054685]
My plug sits about 2 cm deep in foam—how do I plan tool reach?
Plan for a long tubular socket that reaches past 2 cm of insulation. An adjustable wrench will not reach without harming the foam, as reported by the owner. Measure recess depth before selecting the tool. [Elektroda, axl2, post #18051671]
How do I remove the recessed plastic plug without damaging insulation?
Use this 3-step approach:
- Select a tubular socket that fits the cap’s inner hex and clears the insulation.
- Insert it into the cap; engage fully to avoid rounding.
- Turn using the socket’s external hex, keeping the tool square to the cap.
This preserves the foam shell. [Elektroda, Rafikusa, post #18051877]
Should I leave an air cushion in a standing SGW(S) after refilling?
No. Avoid deliberate air pockets because air accelerates corrosion. Some air will appear anyway from water degassing, but do not plan an air space. "There should be no air." Refill normally and bleed where designed. [Elektroda, Michelson, post #18055311]
Where should trapped air be vented in a coil-equipped SGW(S)?
Vent the heating coil via its air vent. Domestic hot water will purge air during use, but the coil needs a proper air vent in the heating circuit. [Elektroda, bumble, post #18055280]
How should I orient the electric heater module when reinstalling?
Install the heater with the cable pointing downward. This respects the thermostat/thermocouple position relative to the heating element for correct control. [Elektroda, Michelson, post #18055311]
Can an anode still look new after 7–8 years?
Yes. One SGW(S) owner reported his anode looked like new after 7–8 years. Water chemistry varies, so confirm with a current test to avoid premature replacement. [Elektroda, axl2, post #18055264]
Is there a video example of this plug/anode service?
A forum post links a video walkthrough relevant to this task. Use it for visual cues on tool engagement and handling. [Elektroda, VPS, post #18053250]
I'll let you know when I unscrew it
