Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!
New radiators installed and system drained - what to do next?
We're renovating our house and as part of that we installed new radiators and a small UFH loop covering 12 m2 in the new extension. The radiators were fully drained first, so all of the glycol that was originally put in when the heat pump was installed is now gone. The plumber is not familiar with heat pumps and said that we should ask the original installers to recommission the system and put the right amount of glycol in.
Now, it's a stupidly cold English June, our heating is off because the radiators have no water in them, and the original installers are taking an age to get back to us.
Is there any way I can fill the system with just cold water and no glycol myself, temporarily, just so the system is up and running while I wait for it to be done with the correct amount of glycol? Or will this run me into problems with warranties and so on? Does the existence of the UFH loop (which was not present when the heat pump was originally installed and has never been turned on) mean that I should just be patient and wait for a professional to look at it all? What would you do in my position?
Can we safely turn on the hot water at least?
(As an aside, it is ridiculous the lack of knowledge about heat pump systems. Surely it's not that difficult for a plumber, who has presumably learnt 95% of the things required to work with heat pumps, to learn the remaining 5%? Anyway.)
ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh
As noone else has replied and its cold, I will do my best to answer you question :-). As long as you dont get freezing temperatures (and your heat pump is off) it should be fine to fill up your system with water. If you wanted to used glycol you can get a cheap refractometer to measure the level of protection you have given it with the concentration used.
I used to use Sentinel X500 in mine but now I have anti-freeze valves instead.
I can’t say what effect this would have on your warranty though so it would be at your own risk so to speak.
House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60
@bontwoody Thanks! Much appreciated!
ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh
@scrchngwsl, while it's tempting to fill the system and get it running during this cool spell, I would advise against it. Since the UFH (underfloor heating) has never been tested, if you fill the system and there's an issue (through no fault of your own), it will be easy for them to place the blame on you. And since the system hasn't been commissioned, if there is an unseen fault, and your heat pump gets damaged, it probably won't be covered by warranty.
I'd exert pressure on the installers coming back ASAP and finishing the installation. And when they come back to commission the system (I'll be curious to hear what they actually do), make sure you insist that they thoroughly balance both your radiators and UFH. Proper commissioning and balancing are crucial to optimal performance and even heating.
🔥 Britain’s Heat Pump Shitshow
How Installing a Heating System Became a National Nervous Breakdown
Free UK shipping.
📗 Heat Pumps Explained
A Jargon-Free Guide for Homeowners
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
New to heat pumps?
Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.
@editor Thanks for that advice Mars. I finally got them to give me a date next week, which is soon enough that we can survive without heating so won't take the risk of messing something up. I'll be sure to get them to balance the rads and UFH too.
ASHP: Mitsubishi Ecodan 8.5kW
PV: 5.2kWp
Battery: 8.2kWh
- 27 Forums
- 2,813 Topics
- 66.6 K Posts
- 1,428 Online
- 7,223 Members
Join Us!
Installer Finder
Degrees of Separation
Latest Posts
-
RE: Should Households Who Can Afford It Pay More for Energy to Help Those Who Can't?
@majordennisbloodnok In most respects, my opinions clos...
By Toodles , 1 hour ago
-
RE: Grant Aerona3 13kw - Buffer Tank - Heating Journey
@heymikey Well done in achieving as nearer a match acro...
By Toodles , 2 hours ago
-
RE: DIY powerflushing tutorial
I didn't throw it away. Is there a way to determine wha...
By bobflux , 3 hours ago
-
RE: Adventures in heat loss calculations
Posted by: @toodles In my experience, energy used to...
By Rob of York , 3 hours ago
-
Grant Aerona - Weather Compensation and Schedules
Im trying to set up a friends Grant Aerona. The WC curv...
By bontwoody , 19 hours ago
-
RE: Why don't people choose heat pumps?
Absolutely nothing in the regs prevents this, nor does ...
By JamesPa , 1 day ago
-
RE: Air-to-Air Heat Pumps & Air Conditioning: UK Heating and Cooling Q&A
@jamespa I agree, the efficiency of Cosy Cooler ought...
By Rob of York , 1 day ago
-
RE: How much of your renewable and home setup would still work if the internet went down?
I think you're right! 🤨
By Transparent , 2 days ago
-
RE: Renewables & Heat Pumps in the News
ECO4 muddies the water somewhat, and then some. I thi...
By cathodeRay , 2 days ago
-
RE: Vaillant ecoTEC Plus - Flow Temp and Set Up
If there is a drain nearby that's exactly what I would ...
By JamesPa , 2 days ago
-
I think that CCGT plant in Lingen is more likely to suc...
By Transparent , 3 days ago
-
RE: Heat Geek installations: share your experiences
@l8again fwiw my experience (Valiant but not with heat ...
By JamesPa , 3 days ago
-
RE: How Can I Prove Coal Was My Main Heating Source Without Receipts?
@etchedpixels thank you for the advice paid cash all...
By Chilli304 , 4 days ago
-
RE: The Changing Jet Stream Could Challenge UK Air Source Heat Pumps
@susannasaunders An interesting conversation to have ...
By Rob of York , 5 days ago
-
RE: Electricity price predictions
@rob-of-york sounds like a term that Heidegger would...
By Papahuhu , 5 days ago





