Alde fluid - my plan

Also Triple Q G13 I understand is not approved by VW to their VW TL 774 J , the definitive G13 spec fluid, recommended by Alde.

There used to be a time when anti-freeze was just anti-freeze. 🤔 This is quite interesting https://www.ato24.de/en/blog/which-coolant-antifreeze

I think you'll find that because the piping between the boiler and the drain plug runs higher than the top of the boiler removing the drain plug will not drain the fluid in the boiler. You have to rely on the new fluid entering the system to drive the old fluid out.

Ok so as a pretty good DIY'r and an Electrician I decided to replace the fluid myself. I have the Compact 3020HE in an Elddis 2018 model Affinity 554. The drain is in the opposite corner to the boiler, and it only drains about 2-3 Litres. My pump is not on the tank but adjacent to the boiler. I then attempted to pump with an awning foot pump against the flow pipe under the expansion tank- no luck, tried the return and it worked but barely.  

In the end it was easiest to follow the advice of an earlier commenter to fit a funnel to the outward flow pipe on the expansion tank and a 20litre bucket on the inward flow pipe. Make sure of a good seal, and it is only this that really takes the time, some jubilee clips and some hose i had in the shed.

Turn on the heating and let the pump do the work. I poured 13 litres of demineralised water (£9- in Asda for 15L) into the funnel as 13 litres was pumped out into my bucket. Do this with the pump on low speed and it takes about 10 mins. The water then flowing into the bucket was no longer blue but clear at 12.5L, i know this because I used 5x2.5litre de-min containers and one spare for a final slug and topping up in a minute- TIME TO STOP.

Empty the bucket then start the pump again, this time filling with 5L of neat Glycol (£20 Car parts online- Spec the same as Alde). When its all in - stop and re-connect up the expansion tank, top up to 1cm above the minimum line with de-min water and start up the heating. 

All good- Remember to note the change date on your Alde service sheet- Mine was on the side of the boiler. Run it for a few hours on high pump speed to push out any air and bleed the two points (more in some vans)- Bathroom Rad and front offside corner in my van. 

I reckon I saved about £200 for a couple of hours work- Very satisfying. And in case you are concerned over the mix strength my manual asks for 60/40 Water/Glycol for -25Deg  protection, or 50/50 maximum mix. I ended up between these two limits so perfect for my use. Take your time and go for it.

Talked to my service engineer, he was shocked that people tried to drain the system before refilling as draining only gets rid of about 20% of fluid and introduces air.

Look on youtube where (https://youtu.be/N7QA8Yutru0 ) where they use a small submersible pump about £9 on ebay. Use the pump to force 50/50 mix into the outflow pipe once the header tank is removed as per hulln000 post.

Tried to get Commer gg40 as recommended by Alde but it looks like it is obsolete will have to use g40 or equivalent. The only worry is that a DIY change might affect trade in or resale value

Draining without a pump does not clear all the fluid granted but opening the bleed screws let's you get the majority out. As the fluids are compatible a little that remains would not do a lot of harm. Yes you introduce air but bleeding the system afterwards removes the air. I would rather bleed the system after changing the fluid rather than bleeding £200 out of my bank account to have it professionally done.