marshian

I have a steel pipe in the same configuration - well actually slightly worse - I have three legs on it 1. Boiler (1m Max) 2. Old gas fire removed and pipe capped (5m Max) 3. Kitchen hob (2.5m Max) It's been like that since the house was built in 1980 - Having a suspended floor and access to underneath I can confirm there has been negligible external corrosion over the past 40 plus years However I've never had boiler cover other than a manufactures warranty (same goes for any other electrical appliance where "extended cover" is available. I effectively self insure I divert a small sum every month to building society account to cover repairs/replacements for anything that breaks. As a result next week I'm replacing my boiler (which is 15 years old) before it fails - I'm not having to fund it on a credit card - it's a well researched choice (my current boiler was probably a poorly researched choice at the time) and is coming out of the "household fund" I've also previously done the same with pet insurance which is always a battle to keep to an affordable level as pets get older (although I recognise that this is probably a higher risk process) It's quite surprising how much people do pay on appliance cover - my neighbour does everything that way and he said his monthly cost was £260 - I put away £100 a month and it seems to work for me I may reduce that once I've paid the balance on the boiler replacement as it'll have a 10 year warranty but as it's going to be down to £550 (ish) I may keep it the same till it's built up above £1000 again

@JohnMo my thanks also for that handy tip - could not work out how to tag users - so simple now you've pointed out how to do it

Yep 100% - I think when the fitting was installed the scale built up around it and the rubber seal gradually degraded - leaving just the scale protecting stopping any potential water from getting thro - the combination of a degraded rubber seal on the back of the fitting sealing it to the tank wall and the gradual removal of the scale prompted the water leak.

We'd lived here 20 years and never had so much of a drop of water on the coldwater tank stand. The boards were soaked, as was the plasterboard beneath it and the loft insulation around it. I think we got lucky as we saw no tell tale marks on the ceiling - I just happened to be going up in the loft for the Xmas Decs.

Oh I missed this bit in your original post - we did exactly that (fitted a water softener) after seeing the scale in the tank It did exactly that - dissolved and removed scale in other parts of the system (in our case the cold water header tank in the loft (outlet fitting) and we had an unexpected surprise a year later)

There is a dilemma there for sure For me prevention is always better than cure - so I'd investigate the internals however I could - Drain down and remove outlet or inlet pipes and use one of those cheap plug in camera probes that work with a phone?

Several years ago I had to replace an immersion on a 118 litre vented copper cyl - the mount for the immersion had clearly been annealed over the life of the cyl and it started to twist and the copper was rucking up - continuing to try to remove the dead immersion heater would have resulted in fracture. It was easier to replace the whole tank so I did for one with an integral foam jacket (old one used to wear two puffer jackets) None of the metal reclamation yards near me would take the tank unless it was opened so I cut it open The level of scale in the tank as a result of moving it around was up to the top of the HW heating coil - the heating coil had maybe 10mm of scale around it. (We are in a hard water area) Explained why we frequently ran out of HW after a bath was run and why heating water used to have to be done at the same time as CH or would have to be done twice a day in the summer for an hour each time Fitting a new tank the water heated in 30 mins and could be done once a day and we haven't ever run out of HW on any day

Viessmann Heat Only 16kW with weather comp and DHWP I did consider the 11kW version but we heat only when needed rather than 24/7 so need a reasonable uplift in output to bring the house up to temp quickly Currently boiler can't do either - I did consider adding a volumiser but I was always going to have issues with short cycling

Very interesting - well documented - I'm not yet ready to go ASHP but I do need to replace the boiler because it's oversize 24kW for the house demand and the short cycle issues waste gas and annoy me even though I've range rated it down to 12kW. The new one will solve a lot of the short cycle issues but spring and autumn will be a challenge when heating required will be less than it's minimum We also prefer to cook with gas so going ASHP (with a grant means we lose that)

I've been data logging the house internal Temps and Humidity as well as the Loft (cold loft relatively well ventilated) Temps and Humidity for the last 10 months but I've spit the data into day/night (based on daylight hours as solar gain has a big impact on loft temps - south facing roof) I did this as I don't have MVHR and when I insulated under my suspended floors to reduce heat loss I saw a spike in humidity levels - I fitted a PIV unit to reduce humidity levels and I've been logging data since It's still not as low as I'd like but it's definately improved the feel of the house.

Very difficult to find the full specs of those atag boilers especially modulation or turndown ratios

We have a suspended ground floor with a sizeable void under it - I've insulated it and it made an absolutely massive difference to heat loss in the house - 4.3 was with an ACH of 0.5 - with default ACH it was around 6 from memory (this winter we were able to validate the 4.3 over a few days when it was around -2 for the whole period) Flow and return are 22mm with short 15mm tails to the rads and I have TRV4 bodies on the rads to adjust flow rates Viessmann 200 isn't suitable - won't fit the desired space - current boiler is 2 pipe flow and return at the top and I don't want to rip floors up to re-pipe for a 4 pipe set up - the difference between 1.8 and 3.2 isn't enough to convince me the upheaval required is justifiable Minimal change to the system required to go to a 100W heat only although the quote I got from the only Viessmann installer in a 50 mile radius is more than expected I'm still going that route. I tried setback with current boiler - it cost way more to run than scheduled heating times (almost certainly due to boiler min kW) I will try it again with Viessman when it's installed. I should add I'm installing with existing vented HW system due to not trusting 30 plus year old pipework with mains pressure I've already found 2 poor joints in the 30 years we've lived here and all the upstairs CH pipes run in the void between the floors and are quite tricky to get at.

I used this https://insulation4less.co.uk/products/tubolit-polyethylene-pipe-insulation-all-sizes I tried to get the OD of both 22mm and 15mm pipe insulation to be the same so I could set up the pipe lagger tool to work with both sizes so that I didn't have to constantly change the width of the cutting box

Looks like they've insulated flow and return together in one bundle - That was done in my house too - I've stripped it all off and insulated each pipe separately - made a massive difference to the return temps at the boiler as there was clearly some heat being lost from the flow to the return pipe driving down the delta at the boiler

If you can read a tape measure and know the construction of your house and the std/age of the double glazing you can do the heat loss calcs for a days work using https://heat-engineer.com/home for a one off fee of £12 I've done it myself early 80's 4 bed detached house (with some 90's insulation upgrades - SUDG, Improved Loft insulation etc) My heat loss at -2 came out at 4.3 kWh - current boiler is 24kW with a very poor modulation ratio (min 10kW) the heat loss explained why it cycles so much as even at -2 it's trying to push 2.5 times the heat required to maintain house temperature. We only have a few days a year at -2 most of the time it's 8-10 deg at which point it's trying to chuck 6 times the heat energy required to maintain the house temp. I've experimented over the winter with flow temps and with the current boiler I can get down to 45 - 48 deg flow temps - however this is mainly due to 10kW min input and a boiler min flow temp of 39 deg C and flow rate of 10L/Min I've also experimented with range rating the boiler to try to replicate what life would be like with a 11kW boiler and the warm up time is a little too long. The heat engineer software has told me exactly what each room needs to maintain a 20 deg room temp and I've been thro room by room sizing the replacement rads to run lower flow temps in preparation to a boiler change this year. (Viessmann 16kW - 100W heat only boiler which will be set up with DHWP and weather compensation - Yes I could go for the 11kW version but the min rating of all the 100W boilers is 3.2 kW so nothing lost by going for a little larger, we heat the house according to a schedule as we are at work during the day and slightly larger improves warm up time) So in summary 100% recommend a good heat loss survey Size your boiler (and rads) according to the way you heat your house and how quickly you want your water recovery to be - if heating constant (low and slow) you can size the boiler to be smaller - if heating according to a schedule you are going to want the boiler to be slightly oversize to get quick recovery of room temps