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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorbogal2
    • CommentTimeJan 16th 2019 edited
     
    At 1st fix stage of commercial Passivhaus vets. Lots of sinks, mainly for hand washing. PH certifier suggests I reduce HW pipework down to 10mm or even 8mm to reduce dead legs, with manifolds very shortly after HW cylinder for sinks with individual runs to each sink between 4 and 9 metres. The void between floors is going to be pumped with Warmcel,

    Firstly, is 10 mm plastic really big enough even for small sinks? My plumbing friend tells me to use 15mm.

    Secondly, would a 15mm pipe with 10mm branching off to individual sinks not be better as a lot of them are in the same direction and they would mostly be encase in 300mm warmcel.

    Thanks!
  1.  
    My WHB is on an 8m run in 10mm plastic pipework and is fine....
  2.  
    Posted By: bogal2Secondly, would a 15mm pipe with 10mm branching off to individual sinks not be better as a lot of them are in the same direction and they would mostly be encase in 300mm warmcel.

    That would depend upon usage. If the basins are in frequent use such that the 15mm pipe doesn't get (much of) a chance to get cold then yes. If the basins are there to comply with the regs. and will only get occasional use then you may be better with dedicated 8mm pipe to each basin. Probably most of the time people will turn the water on to wash hands, pump a bit of disinfectant hand wash gel from the dispenser and wash their hands without waiting for the hot water to arrive anyway.

    You can't use water hot enough to have any effect on bacteria so it's more of a comfort issue. (One study showed that the temperature of the water (40F to 120F) had no effect on the residual bacteria levels). Nor can you have water coming out of the tap hot enough for long enough during the hand wash cycles to have any effect on bacteria in the tap head (e.g. legionella)
    • CommentAuthorDarylP
    • CommentTimeJan 17th 2019
     
    what is the water pressure, static and dynamic? we have plumbed all HWB taps in 10mm Speedfit with no problems... ;-) up to 12m runs.
  3.  
    One of my regrets was not running the kitchen sink in 10mm and that's probably only about a 6m run to the manifold. No issues with 10mm runs in bathrooms and toilet. The one exception I might make would be a utility room sink (where you might be filling a bucket) but ours is very close to the hot water store. Again, will depend on the flow from your tap.

    Remember that to hit the water use targets you're likely to have a fairly low flow tap anyway (at least until it's signed off).
    •  
      CommentAuthordjh
    • CommentTimeJan 17th 2019 edited
     
    Posted By: bogal2Secondly, would a 15mm pipe with 10mm branching off to individual sinks not be better as a lot of them are in the same direction and they would mostly be encase in 300mm warmcel.

    Apart from anything else, the downside is a whole load of extra inaccessible junctions that might fail.

    We're all plumbed in 10 mm.

    As a commercial installation, what are the rules you need to follow about temperatures in the pipes and at the tap? Do you need TMVs at the basins etc?
    • CommentAuthorphiledge
    • CommentTimeJan 17th 2019
     
    As its a vets I guess the basins are going to be in frequent use during the day and users arent going to want to wait for a dribble of flow to wash their hands. If its running at mains pressure go for 10mm or if its gravity pressure go for 15mm. Nice long radius bends and avoid elbows.
    • CommentAuthorbarney
    • CommentTimeJan 17th 2019
     
    Personally, I'd use a recirculating return for the DHWS so you always have 55C - 60C water at the tap location delivered from the HWS cylinder and them mix down with a TMV 2 mixing valve. 15mm copper would be traditional for local WHB's but it really needs a pipe size suitable for the system demand - what's the worst case scenario - say 4 vets all washing hands in separate consulting rooms, simultaneously ? - it may be a lot less than that taking a better account of probability - and from there you can size the return based on the heat loss from the HWS pipework under a period of no demand such as to derive say a 5C temperature difference between the cylinder flow and return

    Regards

    Barney
    • CommentAuthorbogal2
    • CommentTimeJan 17th 2019
     
    Thanks for the advice. Makes me think 10mm runs are a good option. Interestingly I noticed that all the kitchen and basin taps at IKEA come with 15mm flexi hoses but for the whole of the rest of Europe they come with 10mm ones!
  4.  
    It depends on the pressure. If you have a decent pressure (probably a mains pressure system) - small bore is fine. If you have a head tank system - quite possibly not
  5.  
    In Holland they don't have hot water plumbed into their cloakroom sinks. Seems sensible as you barely have the tap running for any length of time to wash your hands, so the hot water just has time to fill the pipe before it's shut off when you're finished, wasting all that heat. I'm looking at this when I renovate our downstairs cloakroom, I might fit an automatic sensor cold water tap.
    •  
      CommentAuthordjh
    • CommentTimeJan 18th 2019 edited
     
    Posted By: Pile-o-StoneIn Holland they don't have hot water plumbed into their cloakroom sinks.

    I believe it's forbidden by law in Frankfurt to supply hot water to a hand wash basin.

    edit: but possibly these sinks are used for rinsing wounds or suchlike where lukewarm might be preferred. Or do vets use sterile water for that?
    • CommentAuthorSimon Still
    • CommentTimeJan 18th 2019 edited
     
    Posted By: Pile-o-StoneIn Holland they don't have hot water plumbed into their cloakroom sinks. Seems sensible as you barely have the tap running for any length of time to wash your hands, so the hot water just has time to fill the pipe before it's shut off when you're finished, wasting all that heat. I'm looking at this when I renovate our downstairs cloakroom, I might fit an automatic sensor cold water tap.


    That's interesting. In my downstairs toilet I fitted a sensor tap (a lovely £1000 designer thing that I picked up for £100 on eBay) which needed a separate mixer. I ran 10mm back to the manifold and used a TMV2 mixing valve there. Since the water in the pipe is premixed the effective deadleg is reduced. The tap runs for 15 seconds and it's warm by the end of that (if the hot water circ has put hot at the manifold)

    That might be a good option for the vets
    •  
      CommentAuthordjh
    • CommentTimeJan 18th 2019
     
    Posted By: Simon StillThe tap runs for 15 seconds

    That's a loong time ...
  6.  
    Posted By: djh
    Posted By: Simon StillThe tap runs for 15 seconds

    That's a loong time ...

    You can probably wash your hands just in time to get the hot water !

    The water standing in the pipe will, in all probability, be at room temp. so I suspect most will not wait for the warm water, just get on with the job. hence the Dutch approach of running cold only to hand wash basins.

    BTW do the regs require hot water to wash hands?
    • CommentAuthorbogal2
    • CommentTimeJan 18th 2019
     
    I like the idea of just cold water to sinks. I cant believe there's much of a hygiene advantage to it being warm- although I remember hearing a doc claiming otherwise once. Not sure if all the female members of staff at work will agree!
    •  
      CommentAuthordjh
    • CommentTimeJan 18th 2019
     
    Posted By: Peter_in_HungaryBTW do the regs require hot water to wash hands?

    I think they may do for commercial premises. Definitely not for domestic though, just convention.
  7.  
    Posted By: djh
    Posted By: Simon StillThe tap runs for 15 seconds

    That's a loong time ...


    I've actually timed it now. 10 seconds I think. The next setting down was 4 and because the sensor isn't under the spout (it's on the wall) it needed to be longer than that.
  8.  
    A related concern: I am looking for a very small pump for a pumped loop DHW feed.

    The pump will be used for maintaining the temperature in a potable DHW loop which will use 10mm pipe (in both directions) in a run of 15m from DHW tank to outlet (kitchen sink). The system will run at 3bar (off mains pressure).

    My gut feeling is that a power of <5W (and the less the better) will be more than sufficient to circulate water around the loop to maintain a sufficient temperature at the outlet. With well insulated runs and essentially zero head, all that needs to be overcome is the drag in the 30m of 10mm pipe, and the flow rate need only be that trickle necessary to compensate for the heat losses. So really, a very few watts will do it I would think?

    With a PIR sensor in the kitchen to trigger the pump with (say) an hour or two of overrun, or perhaps instead a temperature sensor, I think that could be a pretty efficient and effective solution to the tedium of waiting for the water to run hot. (Personally I just use the cold tap for most everything but kids are another matter!)

    So I'm looking for a small pump, which needs to handle potable water, and be quiet? Any voltage, from 240V mains down to 5V dc, could be of interest. Even the 12V units used in camper vans are too big at about 100W, horribly noisy AFAIR and probably don't have the longevity to make it worthwhile.

    The Grundfos COMFORT 15-14 BXS PM (uses 5W on setting 1) for about £150 is the best I've found so far. Almost certainly still too large (it's advertised as being suitable for a loop to every sink in a 2 family house) and rather expensive...

    Any other recommendations?
    • CommentAuthorbarney
    • CommentTimeFeb 8th 2019
     
    I'd use a pump with speed control and run it on return water temperature - if you pick a set point of say 55C (local to the pump) and then just let the pump speed modulate to maintain that 55C condition

    Grundfoss (as one manufacturer of many), can provide it straight out of the box

    Regards

    Barney
    • CommentAuthorMike1
    • CommentTime1 day ago
     
    Posted By: bogal2I like the idea of just cold water to sinks. I cant believe there's much of a hygiene advantage to it being warm- although I remember hearing a doc claiming otherwise once. Not sure if all the female members of staff at work will agree!

    Washing hands in cold water 'as good as hot' : https://www.bbc.com/news/health-40118539
    • CommentAuthortony
    • CommentTime1 day ago
     
    +1
    • CommentAuthorbxman
    • CommentTime1 day ago
     
    A related concern: I am looking for a very small pump for a pumped loop DHW feed.



    no longer Not to sure if this is the one I had in mind .

    never bought from them but I it is the one I had reaserched Ibelieve it is a non ferrous model that will cope with the heat

    http://www.showerpowerbooster.co.uk/shop/

    https://www.showerpowerbooster.co.uk/wp-content/uploads/Shower-Power-Booster-Manual-3.pdf

    think this could be your answer
    good luck
    Patrick
  9.  
    AFAIK shower booster pumps work by detecting a flow (pressure drop) then switching on and pressure build-up when flow stops switches it off, whereas what will be needed for a DHW loop is a continuously running pump. (Perhaps a timer switch for off over night??)

    Would a small central heating pump work? They are impeller pumps which should allow through circulation if there is enough pressure behind the DHW to get enough flow at the tap. Perhaps a trial if you have an old one around or maybe someone here can advise.
    •  
      CommentAuthordjh
    • CommentTime23 hours ago
     
    Looks like an interesting product and there is a manual variant as well as an automatic flow-controlled version, so I don't think that's an issue. But all the suggested applications are for intermittent use, whilst a pumped loop will likely be on for much longer, depending on how exactly it is controlled. So I would check suitability with the manufacturer first.
    • CommentAuthortony
    • CommentTime13 hours ago
     
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