crooksey

Should be fine, all down to what building controller is happy with. Probably look at it once and just nod. Two bathrooms upstairs and one downstairs on the same stack isnt un-common. Added utility sink and washing machine isn't adding much into the mix.

If you want to do it properly just dig it out, no magic cure i'm afraid. If I turned up to a job and had to finish it no fail, I would disc cut the clay pipe flat with the floor, put a flexi adapter on the new pan and force it into the clay.

Doesnt matter about DPC whats the floor height from that concrete base as pictured to the existing floor level? As thats what you are governed by. Floating chipboard is fine over celotex, glue joints etc. More people prefer screed now as you can embed wet UFH in much easier.

In that case why not get the septic tank cleaned out and emptied, divert all gutters do it, then only have a foul sewer and use the culvert for rainwater. Will also lower your water rates as you will only be paying for sewage and not rainwater.

New rules means you cannot discharge a septic tank to a culvert, unless it ends up in a drainage field (highly unlikely), you will need to replace this with a sewage plant (and then continue to use the culvert). I would route all down-pipes into pipework AFTER the sewage plant, so you don't get any issues. Also I would an an NRV after the plant to if the culvert was to become blocked/overfilled in heavy rain it cant back flood it. Probably not the news you wanted, but its the law now (since 2020).

That doesn't look like it has enough height for PIR and then 50mm of screed? Whats the height difference to the original subfloor? If its a new extension, building regs probably want a decent amount (150min) and up stands, and looking at your patio doors, doesn't look anywhere near enough? You may have to insulate and then float chipboard over it to get the required U value.

With a suspended floor you can have overlay systems that use a self levelling compoud to encapsulate the pipes to create some form of thermal mass, but its basic physics. If you dont have anything to store the heat, the room will feel cold quickly, much like a well insulated house with radiators, as soon as they turn off it feels noticeably colder, but not necessarily "cold". A 1930's house I imagine is nowhere near "air tight" standards, so you are probably losing a lot of generated heat to small draughts.

You have nothing to retain the heat then. So once you switch it off, the heat just dissipates into the air. Thats why in most specified UFH installs you have a screed to encapsulate the heat and retain it once the UFH is switched off. Would explain exactly why it does not feel warm when the heating goes off as you have no thermal mass to store the generated heated

What do you have as a floor screed? Gypsum/Anhydrite based screeds or ones overlaid with wood can warm up quickly, but not retain much heat, giving the feeling you describe above. However sand and cement or thicker cement based liquid screeds retain the heat for much longer, acting as an all day thermal store and can be harder to tell when the UFH is on, unless you stone/tiles/bonded LVT etc.

LVT over SPC everytime. LVT is permanently bonded and has a very small failure rate, SPC is a floating floor and is much more prone to failure, broken joints, over expansion etc. LVT is fine with UFH, all the glues are rated to a slab temp of 35C, which is very unlikely to be exceeded, unless you have a very thin gypsum screed and a very high flow temp on the UFH. Its all the same underfoot as porcelain, if you want something "softer", look at engineered wood.

I would be specify air to air or infared heating, underfloor doesn't really suit the spec.

Soil pipes leaking is very rare, they are sealed pipes, so the toilet/sink would leak and not the pipe (if installed correctly). Usually box in with two layers of acoustic plasterboard and some acoustic insulation inside. Bad call from the architect placing in the living room though.

Running them externally also creates a weak point for insulation/draught proofing. Much better to run them inside, any decent architect will have designed them in a way to be out of sight by the time all walls are up etc.

If its your ditch, you can make it deeper/clean it out and good management of it will solve nearly all your problems. Could you add in a culvert/new ditch to feed the main one at the rear of the property? Any pipes entering a ditch I would add a NRV (non return valve) to.

Glue (+nail if you can) the board down, wont need an expansion gap then.

From experience the water board are sticklers for the rules, might get lucky but personally I wouldn't chance it. If they cotton on its the wrong chamber they could potentially start to question or ask for further areas to be re-exposed which is hassle you don't need.

Once you have had it a few years, you probably will never check it and just get it checked once a year on a service and pump out. Yes you can go longer, but for the amount saved having a pump out, jet down and inspection once a year is the best practice and if god forbid you ever need a warranty claim or house insurance claim, following the rules can save a fortune in the long run.

About two times a year, you can get unpredictable levels of sludge, and/or in some drain-fields you can also get reduced drainage, I usually find its between winter into spring and summer into autumn. I have no idea why, but on a number of jobs I have seen this/heard it from customers. Not when I have been involved in the drainage, but as a comment from a customer, or an observation when working there. Usually short lived but I always had it down to bacteria reacting to ground temperature changes.

Puraflow can be a stand alone unit, what I meant was, why not have a PTP then a puraflow, as opposed to a septic tank first.

Other than for conversion of existing septic tanks, I would struggle to see the benefit to this over a packaged treatment plant? That produce water clean enough to discharge to a watercourse. Unless the irish regs are different..

Also TF170 at 150mm will be fine, may be cheaper to install eco therm (or others) at 200mm though.

I run an ASHP and pay around £200 a month for my entire electric bill (summer is much cheaper), mines been refitted to an older property with insulation that wouldn't be the same as a new build. Been in over a year and im well impressed. Replaced an old LPG system. They work so well with UFH and for a new build, I just (personally) do not see any benefit in choosing oil fired heating. Go with 125mm pipe centres (nice low flow temp) . Get a decent screed over it, avoid solar thermal water heating, if funds allow go for solar PV to help run the ASHP. Personally I don't like burying water pipes in screed, go through the walls or ceilings where possible for future remedial works. I was very sceptical but had an old LPG system that was toast, was installing new UFH and screed (was very skeptical and again doing the work myself) but have been very impressed. If you really want oil I would just future proof your install with low pipe centres (125/100) and then put a decent manifold in so you can control the flow temp (not sure if oil boilers allow the same level of flow temp as a ASHP).

I have a longer run outside, covered in the same way. We run a flow temp of 35C and even last year in -6 we had no issue. As others have said, pipes run is a bit strange, usually you want them tight to the wall, not the rear of the unit.

Dig a bigger hole and put some dry 5:1 mix in with the shingle then, its not rocket science it all depends on exact site conditions. Again, anything a decent crew will overcome on the job.

Decent ground management and a number of pumps, problem solved. Especially with plants like a graf where you secure them with shingle, as opposed to concrete. I would also want the riser 100mm above ground level (if the table was really high)