RossMcO

@JamesP~Thanks James, Vortex hadn't made my list until you mentioned them. For the others, and to keep you all up to date, I'm trying to get in touch with the company that the architect uses for SEPA calculations, so far haven't had a response to email, but will keep on at them. From their web-site, they seem to be Kingspan reps, so that might go some way to explaining their recommendation. I think all of the systems will do the job, and the majority of the cost is installation (at least in my location and with the quotes I have) so it's not really an economic decision. I favour the aerator system whether from Graf, Marsh or Vortex might end up being as much to do with local supplier and support as anything else.

For 'tiny', I'm reading 'low' use. The challenge is that while there will be empty periods, there will also be periods of potentially full occupancy, so up to 8 adults, plus any weans that emerge in time. That will drive periods of heavy usage, so we will need to size the system to cope with that while trying to make sure we avoid issues related to low flow periods. @Russell griffiths's experience seems to be that it isn't such a major issue, and I'll have other things to worry about more. 🙂

Thanks Russell, that's a very helpful data point. To @SteamyTea's additional fluid question - this also seems rational to me. Maybe I could have someone go in and flush everything a couple of times once a month or every couple of weeks, or try and rig a system to run water from some source or another periodically.

@Russell griffiths perhaps, and I applied little critical thinking to the comments from the supplier, but...he wasn't buying or selling, all servicing would be from a third party, so he was a relatively honest broker. My situation at least initially will be complicated by long absences, and having confidence that I won't arrive to find a non-functioning system has value. Also, I suspect he was overestimating the dosing required, as if there might never be any use, rather than occasional longer gaps. So maybe one cartridge per year, and an inspection/pump out as needed. Do average users normally have a service contract to cover inspection and any maintenance needed? In general though, I agree with you - I'm starting to get a better appreciation of the complexity, or lack thereof, of the different systems. Simpler is better, fewer mechanical parts better than more, simple service access better than in tank components, no electricity better than power being needed. But, beyond all of that, the real life experiences of the community carry most weight, and at least for the active posters on this topic, aerated systems seem to be much preferred. Ross.

Hoping to have PV, but will need another building for that, as our monopitch roof is north facing. National Park rules prohibit any new structures without explicit permission. Consensus of the discussion remains on the aerated system. Cheers.

Completely agree on his contribution - tremendous benefit. Touch wood, I don't have that problem (as of now) but what a fantastic shift of the accepted wisdom.

Have to say, I'm closer to @Alan Ambrose on this one, versus the extreme option of distilling and potentially drinking your own 'liquor', I believe one of the technical terms to be? But, Barry Marshall got a Nobel prize for his work, so @saveasteading and @SteamyTea should be at least worthy of something similar on successful conclusion of their experiment. 🙂 Photographic/video evidence required mind... Back to reality. On the topic of longevity, I guess you could just pre-purchase the bags for the next load, and give yourself ~20 years of service. Depth might be an issue - our site does slope downwards to the water course, but more work would be needed to figure out whether we have sufficient gradient to accommodate outflow to the tank, and then another 2m to the outflow from the tank, and then sufficient drop to the water course. An earlier topic the forum discussed running costs and maintenance, so to add a little bit of information to that discussion, for an aerated tank, for a 9 person Graf system, and intermittent use the estimate was 2 carbon cartridges at £150 per year plus ~£200 service visit per year. So, an additional £500 annually plus whatever power costs may be. This is not the primary consideration for me as a non-functioning or mal-fiunctioning system would soon consume that much money in call-out costs and aggravation, but I add it here just for the wider knowledge pool. From all of the discussions above, my summary is: Biodisc, not widely recommended due to mechanical elements. Aerated: simple easily maintained, but will need careful management and additional expense if left unused for extended periods. Biorock: maybe, but concerns over depth for gravity feed, consumables, and little/no experience of its use on the site. I still have some more calls to make, but at the moment, I would be opting for Graf or similar and building in the additional maintenance costs.

@saveasteading there is a fair amount of first order data on their website, and this video as a high level explanation I didn’t find any detail on the make up of their media, but not sure I would expect them to be explicit on that in a public forum anyway. Seems interesting as it has even fewer moving parts than the Graf system. Ross

Thanks John, We have SEPA approval, so if I chose to change horses at this stage it will require resubmission. Since my last note, and guided by the above discussion, I've had some more conversations with architect and Graf, and the plot thickens. Given the intermittent use, Graf UK recommended that I consider a third system: Biorock https://biorock.com/products/small-sized-systems/ecorock, which if we can manage gravity outflow, can be an unpowered system, and would not need regular dosing as per the Graf One2Pure tank. This approach on one hand is attractive as there are no ongoing running costs, but on the other hand, is it a bit of a retrograde step - it looks like a traditional septic tank with an added aerobic filtration system (filtration media lifetime claimed as <10 years)? Does anyone have experience of the BioRock system? Ross.

@SteamyTea I guess it’s good they had somewhere to go somewhere. Bad news is if they all stayed there together and fostered their collective incompetence. 🥴

Thanks, for the comments. @crooksey gravity fall should be straight forward, the slight has a healthy slope. The non-return-valve sounds like a sensible precaution, so I will talk that through with the groundworks contractor. @Kelvin @saveasteading don’t want to do the architect a dis-service- it was spec’d to the model/part number and SEPA approved, I was just being a bit lazy with shorthand.

Thanks Russel, I’ve been in touch with Graf by email, and hope to have a call with them this week. I’ll ask about their options for additional bacteria dosing.

Thanks. Yes, single story mono pitch, with high side almost due south. Lots of glazing on south side, with all rooms opening to that elevation.

To close the loop on this topic (with thanks to BMJ1 for his help via DM). British Gas were the most responsive, and were able to install the meter pretty much on demand, given that my request went in on 27th or so of Dec and they were able to install in the week of 6th January. @Canski I get the call support issues - took several rounds to get to the installer team but from then on, they did exactly as promised. From other discussions on the site, I've opted for a standard tariff with no cancellation fee, so I'll stay on that for the duration of the build and then work out the best tariff once domestic usage stabilises. Thanks for the comments. Ross.

We are building in a National Park in Scotland (site plan allatched), and have approved plans to install a Klargester Biodosc system to treat our waste water before discharging to a water course on site. We were not involved at the point that the Klargester system was specified. From reading the forum, I've been convinced that the air bubbler systems make more sense than the Klargester mechanical agitation system, so thanks to everyone for the education so far. My next task is to select an alternative system and convince my architect & groundwork contractor (and SEPA?) to alter the intended plan. But before then, I have a question for the forum. This house will hopefully serve as out retirement home, but until then will only see occasional use. We live in Germany full time, and it is likely that the house will be unoccupied for up to three months at a time. Reading the different threads, there is a lot of discussion about cycling the pumps to best manage electricity consumption and treatment efficiency, but what happens if there is no new foul or grey water input for two three months? Does anyone have experience of an intermittently used system, or strategies for managing the unoccupied periods? Any advice on one system or supplier over another in this use case? Thanks in advance, Ross. Site Plan.pdf