Russdl

Ah, I think I've spotted where we are diverging here. My theoretical system is a: Genvex Combi producing hot water at a suitable temperature for the UFH whilst also dealing with the MHRV requirements of the house. Sunamp being charged by Solar PV and off peak electricity. The Genevex providing pre heated water to the Sunamp (instead of a cold supply) so that the Sunamp has less to do to get the temperature up to that required for DHW. Is that what you understood by my original question?

@Nickfromwales Doh! Thanks. @PeterW But would it need a massive heat output as the Sunamp (in my theoretical set up) would be boosting the DHW temperature?

Sorry @PeterW, 'small mono' what is that?

Thanks for that information @PeterStarck. Good question @Nickfromwales. If a Genvex Combi feeding a Sunamp isn't a ludicrous suggestion it seems to me that it would be quiet an elegant solution to all the DHW and ventilation needs of a home.

Back to Sunamps (ish) and working on the assumption that the only stupid question is the one that wasn't asked ? Would the combination of a Genvex Combi and a Sunamp be ridiculous (price alone?) The Genvex prioritises hot water with the heat pump and then gets on with its MHRV job, as I understand. Can the Genvex hot water temperature be dialled down to make it more suitable for UFH and as a pre-heat to a Sunamp and if so what are the reasons why such a set up would be ridiculous (price alone? I bet there are more) I guess the Genvex would have to go to a higher temperature every so often to prevent Legionella? Standing by...

So it seems my mind is made up in one aspect; rodding access from the start of the drainage run, but can I ask (especially you @epsilonGreedy) how exactly did you do it?

? Two very good points there @PeterW along the lines of my concern over the pong but much more tactile. Outside rodding it is!

@PeterW I like the idea of a rodding eye on the end of the main run, however it would appear simpler to having a rodding access point at the base of each stack. Apart from ensuring they were easily accessible what are the draw backs with such a solution? (Stinking the house out when it comes to rodding just sprung to my mind). Any other reasons why the rodding access shouldn't be inside the house at the base of the stack?

You've clearly had plenty to deal with in the last two weeks Vivien and kept things on track. Well done you. I may well be free on the 30th & 14th, if I am I'd appreciate the opportunity to visit when the foundation is started and the frame arrives. Russ.

@MikeSharp01 No problem! It got me looking at things I hadn't properly considered and hopefully my interpretation is correct.

@Temp Thanks, another thing that had been on my mind.

That would be the plan. I think I got the idea from here, did you post a picture of your rainwater solution? If so that was my inspiration but I also don't know if its acceptable for foul runs. Failing that then i would plan on access at the base of each stack prior to finished floor level. Neither of those solutions have been properly thought through yet... That wasn't the driving force for me but would be an unintended consequence if I opted for my blue route. @epsilonGreedy Pointed out the obvious requirement for the rest bend at the base of the stack - so obvious that I hadn't taken it into account. The remaining fall could start to get tight now and the shortest route may be the only option (apart from all the other options that I have no knowledge of!)

Of course! And the architects route would need at least 3 IC's for the same reason, plus 1 more for where the two drains meet and yet 1 more for the max 11m run (if that is the limit) So assuming @MikeSharp01's correct r the max 11m (I'll get on to checking that right now) the IC count would be: 5 for the architects route 3 for the developers red route 2 for my blue route If the 11m rule is correct, all plans will have an IC some point on the lawn between the hose and remaining drain. So on the IC count the blue route would win. Any other views on running foul drains that far under a passive type slab construction? ~~~~~~~ According to Approved Document H, if I've interpreted Table 13 correctly then the stack to the first IC can be up to 22 meters (or bananas, it actually doesn't mention meters anywhere on that table) and then from IC to IC/Manhole maximum 45. So that would reduce at least 1 IC from all the options. Doc H does say "The layout of the drainage system should be kept simple. Changes of direction ... should be minimised" The architects plan does the opposite. Ant thing else I'm missing?

So far it seems like the architects plans or my developer friends plans are winning. The developers version seems much simpler than the architects, any ideas why the architect would have chosen the long way round save for some comments already posted?

I'd considered that, and the first IC would be under decking/patio and disguised as such. I hadn't considered @MikeSharp01's comment about the max 11m run, which would indeed place an IC chamber in the lawn or a flower bed so your point is taken, thanks.

@MikeSharp01 Another good point that I should probably have been aware of, thanks!

Good question, well phrased... I think it was to get everything pointing in the right direction, i.e. heading towards the existing drain and keep it simple but I take your points re minimising long foul runs under the slab. Thanks for the input.

I'm after your collective wisdom again! On the attached image the architects foul water plan in dotted lines (I hope the quality is good enough to see it) goes clockwise around the outside of the proposed property to the existing sewage connection. A developer friend of mine suggested the route marked in red from the two stacks, the opposite way round to the architect. I'd considered the route in blue on the diagram (the red and blue lines converge where the stacks will be) It would be under a passive slab foundation and the width of the slab is 7.5m. The Invert Level of the existing drain is 60.66m OSBM and the finished floor level needs to be 61.88 OSBM, so, takeaway about .450m for the floor and slab leaves 61.43 OSBM, or .77m fall between the underside of the slab and the existing Invert Level. On my blue lines the longest distance between stack and existing drain is about 25m so (if I'm right) there is sufficient fall. I hope I've used all the correct terminology... Are there any reasons why one proposal trumps the other?

Excellent, I shall relax - slightly - again.

@ProDave Ok. I'll obviously be getting an electrician on board (it would seem sooner rather than later would be the order of the day). My preliminary plan would have the new supply about 12m from plant room where the supply would emerge in the new build.

@JSHarris Today is definitely a school day, I'm learning loads! I recall seeing pictures of your set up in your blog and I certainly plan to do something similar. Now I'd better get on and find out more about that BS7671

@jack Oh Lord! Just when I thought I was emerging from the woods. ? Thanks for the 'heads-up' Jack, I'll check it out.

@JSHarris Thanks for the re-assurance. I'll make a note of all you've said especially the TT earthing system (when I've found out what that is) and make sure I don't run it as a TN-C-S (whatever that is!) ? It's sometimes embarrassing to be this thick but I'm starting to get used to it ?

@ProDave Indeed, that's exactly want I plan to do after seeing various BH members doing it. I hope I've not stitched myself up by calling it a 'temporary building supply' when I was talking to the DNO, but I made it very clear that the temporary supply will be in a permanent position just inside the plot and the new house will be connected to the temporary supply at a later date.

Ah, the wonderful enlightenment of Buildhub. We your advice on-board I phoned the DNO again, the existing supply can provide up to 23kVa so as Dave suggested I've told them I'll need 10kW for the TBS which is just a figure they needed to put in a box before they can move forward. That hurdle seems to be jumped. Thanks again all for your help as ever. Russ.