There was a brief discussion about just that in a recent RNZ Media Watch podcast. Get it while it’s still online.
Which episode is it in?
So I think in the public interest, I might invest in a bit more plumbing (so I can bypass our drainwater heat exchanger), and update with some data, both on how much money is saved, and how much efficiency is reduced through fouling.
Either way, you should definitely install it so that it can be easily cleaned (hopefully just a single grub screw that allows you to remove the final plastic section
As you'll see above, not strictly gravity film, and and at least some very mild corrugations to induce turbulence, which enables it to be installed in a near horizontal position. And we will be installing near horizontally. The current shower waste is all copper(!), but given what you've written, I think I'll get the plumber to put in a Y regular joint, and use the straight access for cleaning. Will update once installed!
(PS - thanks for the advice! get well soon)
I remember this article: I bored Beloved senseless about it. Where can the systems be obtained?
I bought ours from a napier company ($425 incl freight)
However, you should probably also read David's comments re: mounting and the inner surface, as on closer inspection, it does seem like this one does have a slightly irregular inner surface, but can be installed in a more horizontal position.
The (better?) gravity film ones are more expensive and can be sourced here
David's is the first piece of skepticism I've come across, so I'm super keen to hear to!
(Plus, I've actually bought, but not yet installed one).
I've spent a lot of time investigating this as, on the face of it, it just seems like a no brainer. And so we wait :) :)
I’ve done heaps of modelling on these systems and they are good in theory. The problem is the HX cost and the cleaning. Most systems use some sort of horrible draino-type stuff every few weeks.
As we are about to install one, I'm curious about the cleaning issue (many claim to require no cleaning). Is it that the kind of scum that normally builds up in drain pipework reduces the HX efficiency, or another kind of problem? Would we be wise to plumb it in so that it could be mechanically cleaned (with an oversize bottle brush)?
Similar savings to solar
This isn't spam, I'm just so frustrated that this isn't in the frame. Basically the only people drain water heat recover isn't good for is if you have a new house with a concrete floor and your shower drain is inaccessible. Or if your house has exceptionally restrained showerers.
If you are interested in cutting your hot water energy costs, and showering is a big consumer of hot water, you should do this first: drain water heat recovery. Essentially, it's a heat exchanger that goes in the waste pipe below your shower, that uses the heat from that water to pre-heat the cold (either for a cylinder, or straight back to the shower). I wrote a long post about it here. The Napier company sell them for under $500, and they cost about $200 to install, and confer about the same savings as a solar system.
I just don't understand why we are still talking about solar*, and not this. Except I guess drain water is yucky.
*Of course solar is still a good thing, but if you put one of these in, you can install a smaller system.
I'm putting this in a separate post, in case Russell or Graeme think it's better moderated.
One of the things that I dislike about the current regime is that there might be some questions that might be worthy of public discussion, that are less able to be discussed (or I feel are less able to be discussed) because of these rules. For example: Are the rates of alcoholism and mental health issues that I anecdotally perceive in criminal defence lawyers acceptable, and what can we do about this? It's not the best example, but it's the one that springs to mind.
In recent months, I’ve seen the Herald do something very interesting. When there’s a story involving a suicide they can’t mention, the article proceeds as per usual (“no suspicious circumstances”, etc), but at the end there’s a list called “Where to get help” with the contact numbers of various agencies such as Lifeline and the Suicide Crisis Helpline.
Assuming law change is not forthcoming, I appreciate this sleight of hand in contrast to the "[there were no suspicious circumstances] this death has been referred to the coroner", which always leaves a small margin of doubt in my mind that perhaps I'm not accurately reading between the lines.