Crofter

From memory, a treatment plant would only allow me to reduce the size of the soakaway. The Puraflo let me almost completely eliminate it.

I'm not aware of Scottish regs allowing for anything other than 110mm. It seemed complete overkill for a single toilet on the ground floor.

I installed a Puraflow system. Comprises conventional septic tank, pump chamber, then the clever bit which is the Puraflow unit itself. A big plastic tub filled with peat moss fibres and some piping. The effluent is pumped around that and trickles down through the peat moss, which allows for aerated breakdown, and what emerges from the holes in the bottom is fit to discharge to ground or watercourse. The system was designed in Ireland where high water tables are a very common problem.

Yes I'm not recommending it as a solution to other people. And I was a bit wary of it to start with. The backup option would have been an AAV on the rodding eye, but that seemed like extra complication. I was really loathe to install a big clunky soil stack on a fairly visible elevation.

Btw, talking about soil pipes, when I was building the cottage I learned that the 110mm standard stack is mandated for anything from a single WC up to four bathrooms. I found it hard to imagine that a single toilet could generate so much of a vacuum that it needed a 110mm vent. So I didn't fit one. I wasn't bound by building regs and this was one of the only places where I deviated deliberately. I used a 50mm pipe instead, which meant I could run it hidden behind the larch cladding. Five years on and it's working perfectly.

I'm a bit surprised about the freezing comments. The only place where there should be standing water is in the traps, and surely they are all inside the building?

I've been looking in to this too. My background is off grid low voltage systems so my first thought was to go that route. But I think grid tie actually makes more sense. AFAIK your options are: - panels, battery, and LV heating element - panels, battery, inverter, AC heating element - panels, grid tie inverter, solar diverter, AC heating element. It seems that you can't skip the battery if you want to go off grid, you need it as a sort of buffer to keep the system running. The last option is the one I'm going to go with. Grid tie inverters aren't much more expensive than off grid ones, and it simplifies things hugely to be able to use the existing AC heating element in the tank.

I'm aware that this could be a risk. Trying to get an idea of what would actually happen in practice. I'm assuming that if I modify the system to add E/W panels, but keep the peak output within the original limit, I should be ok?

I'm not actually planning on sticking with a 2kw system. Just want to get the MCS cert so that I can get export, then I'll add additional panels later. Partly this is due to cost savings, and partly because I may need to do some work on my roof first. I've run numbers and should be able to get around 747kwhr/yr per installed KW, on a S-facing ground mount. Mixing it up a bit to include the E/W house roof gives me an average of 675kwhr/yr per kw.

I'm planning the cheapest possible MCS installation. Ground mount would be preferred, because my roof is E/W and also my roof (on the older house) isn't in the best condition. Of course panels are so cheap that I'm not sure how much I will save by skimping on them, even at MCS prices. But for sake of argument let's say 2kw. With a 3.68kw inverter installed for future proofing.

I'm trying to get an idea of the basic starting price for an MCS system. So far I don't have anything to compare with. I know it will vary enormously by specification and location, but for a small ground mounted system do you think ~£5k is realistic?

I'm not sure my guests will appreciate me turning things on and off remotely! I could maybe get away with it for the DHW but that would be on a diverter anyway.

My situation is maybe a bit unusual/complex. I've got two properties and would like to add PV to both, if I can afford it. First house: 70s bungalow with storage heaters and direct UVC. Currently used as a holiday let, mostly in summer. Bills included in rental so no incentive for guests to save energy. I'm planning to install A2A heating and perhaps PV with a diverter to the tank. Our longer term plans involve moving in to this house ourselves. Second house: 43m² holiday cottage (see my profile pic) used exclusively for short term lets, again mostly summer. High standard of insulation. Direct UVC. Again, thinking of PV+diverter to heat the tank. Because we aren't currently living in either house, we can't rely on managing loads etc. Whatever I install has to be hands-off and idiot proof. Being eligible for export is appealing because at least I'm guaranteed some sort of return. But if it doubles the cost of the project, then maybe not.

Which I'd be fine with, but it means no export.

Not having much luck finding someone who covers Skye

I'm specifically trying to determine the lowest cost MCS installed system. Panels are basically free these days. So why pay somebody else to source and install them? Of course the MCS guys can maybe get the panels even cheaper than I can, despite their profit margin.

Hypothetically... if I were to get a small/minimal ground mounted S-facing PV system installed by an MCS contractor, in practise could I later add extra panels facing E/W? I'm assuming that my export payments would be limited to whatever the original installation had, but with the extra panels I would get a longer generating day. And (how long is a piece of string) what kind of cost would a minimal system be?

That immersion looks good but it's really really expensive. I'm thinking the Cool Energy DiverTech will do the job at a third of the cost.

Thanks, so basically it's the same as most wiring then- don't be an idiot! And the requirement to get it done by an MCS company still stands if you want to get paid for export?

Sorry I was assuming that it would be at that point that I would be rumbled and they'd all me who was installing it.

I like to DIY 🙂

I'm playing around with various ideas just now. Full picture: We have two properties, either side if the road from each other. Both on electric for everything, no mains gas here. The older one is a 3 bed bungalow, with ample space behind it for a ground mounted array, and E/W roof. The roof is made from some delicate looking felt type tiles, and I really don't want to mess around with it. The other house is the one on my profile pic, 1 bed built under the 'portable building' exemption so no building warrant (it does have PP). Also has E/W roof. It's corrugated steel on battens and I'd be quite happy to mess around up there and add panels- I did design and build it, after all. At the moment both are used as holiday lets, because we're living on our boat (how's that for off grid 🤣). We're likely to move back in to the bigger house for a while and then, hopefully, go back to boat life again in the future- for the summers at least. So anything I install should be idiot proof and need no manual intervention. The primary aim is to get the bills down. I also think it would be a good selling point to be able to offer free EV charging, although I'm not convinced the ROI adds up there. At the moment I'm thinking about a ground mounted array on the bigger house, and roof mount on the other one. Both designed to feed a 16A diverter which would offset daytime loads and use the immersion heaters as a dump.

You say after the event... what happens if you 'forget'? Would it just come up when you came to sell the house?

Another question: If I get my panels, inverter, and diverter, what regs, rules, notifications etc are involved? I understand that without going MCS I can't get paid for export? And I believe on systems larger than 4kw you have to notify the DNO? But assuming I don't go down the MCS route, what else do I need to do? BCO sign off? Qualified electrician to connect grid tie inverter?

On E7, it makes sense to feed the house first, because I'm replacing 40p/kwhr electricity during the day. If I don't get the tank heated up, it will just boost overnight at 16p/kwhr.