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Ecodan Cylinder Possible Weeping Around Thermostat Port

 
Domestic Hot Water & Cylinders
Last Post by Gruff2001 4 weeks ago
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 Gruff2001
(@gruff2001)
Active Member Member
Joined: 3 years ago
Posts: 8
Topic starter 24/02/2026 6:10 pm  

2.5 years of use and I’ve just spotted a white residue around the thermostat port, wasn’t there a month ago

I’ve contacted the installer, a fitter got back to me and said there’s  nothing to worry about it’s just a glue residue that sometimes develops.  To confuse things, a higher up in the firm emailed me saying it isn’t right and that I should contact Mitsubishi.

Clearly this isn’t helpful and I will be contacting them again when business is open.  Before then I’d like to be as informed as possible.  Could anyone shed some light on this? Thanks in anticipation

IMG 0690

 

G


Ecodan 6kW, 5.4 kW PV array, 9.6 kWh GivEnergy battery, Bosch induction hob, Zappi 7kW charger, electric car and electric motorbike


   
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 ASHP-BOBBA
(@ashp-bobba)
Honorable Member Member Professional Installer
Joined: 1 year ago
Posts: 431
26/02/2026 12:09 am  

This is likely thread sealant for the pocket plug, very easy fix if it starts oozing out, unless you get an actual leak it is probably fine, what you could do is ask the installer to remove the white trim cover cap and just make sure the joint is not leaking into the insulation.


AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.


   
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 Gruff2001
(@gruff2001)
Active Member Member
Joined: 3 years ago
Posts: 8
Topic starter 12/03/2026 1:59 pm  

Update:

Mitsubishi sent an engineer around. It was limescale from seepage.  Removed plug, cleaned etc, etc

Root cause most likely under-pressured DHW expansion vessel (system serviced 6mths ago).  Fingers crossed it’s now sorted


Ecodan 6kW, 5.4 kW PV array, 9.6 kWh GivEnergy battery, Bosch induction hob, Zappi 7kW charger, electric car and electric motorbike


   
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