On 22 April 2020 the USA EPA / EWRI (as part of the ASCE) held a kick-off meeting on Premise Plumbing Modelling (PPM). The original plan was to have a 1.5 days workshop with experts from around the world. Due to the COVID-19 travelling restrictions, instead a webinar was held as a kick-off to launch the newly established PPM task committee on this subject. The purpose of the task committee is to ”advance the science of the new field of premise plumbing modelling and to help develop building water systems management tools for use by practicing engineers, as well as the larger water distribution research community in support of the safe design and operation of water distribution systems”.
The meeting was from 16.00 – 18.00 CET, so people at the USA west coast had an early morning, and someone in Australia had a late night. There were 45 participants, with 5 technical talks on various important aspects of PPM.
As most participants have a background in Water Distribution System modelling, it’s interesting to look at the modelling differences between the two, see table below, which was a result from the pre-webinar survey the participants filled out. The five speakers addressed most of these aspects, plus more.
Tom Walski (Bentley Systems)
Tom Walski spoke about the use of a hydraulic network simulator as it is widely used for WDS modelling also for PPM. This can be done, and has been done already. As KWR we also have some experience in this. There are some drawbacks, however, e.g. in generating the models which at the moment is done manually. His talk touched on items 2 and 5 in the table.
Mirjam Blokker (KWR)
Mirjam addressed the demand modelling part. For PPM modelling you need to be able to model demand per tap, even per tap for cold and hot water, and the time scale also needs to be very small since most of the time there is no demand, and then there are some bursts of short demand (e.g. a few seconds for washing your hands). SIMDEUM is an established tool for this, with extensive validation. Mirjam showed how it works, and various applications of PPM such as temperature modelling, sizing of water meters and pipes, and also linked to in-home sewer modelling. Her part touched on items 2, 5, 6, 7 and 8 in the table.
Michèle Prévost (Polytechnique Montréal)
Michèle gave an overview of water quality issues building water systems. The effect of stagnant water on lead release and microbial contamination, Legionella and temperature, and residual chlorine were examples of the aspects she has studied. Her talk touched on items 6 and 8 in the table.
Gary Klein (Gary Klein and associates)
Gary presented the main interest of premise plumbing design: customer satisfaction. People want enough water from the shower and with the right temperature, without having to wait for it too long, without sudden pressure drops, with also hot water available to the third or fourth person in line to take a shower. People also want their toilets to flush the first time, every time. They want clean clothes and dishes. Gary has measured a lot of pressure versus flow rates of store bought appliances, and noted that the flows are in practice very much lower than what is promised because pressures are in practice lower than the nominal values. His talk touched on items 7, 8 and 9 in the table.
Walter Grayman (Consulting Engineer)
Walter presented a vision on a hydraulic network simulator for PPM. A PPM-EPANET would need engine and interface modifications. The engine would need to updated for different demand representation with a difference between user defined and volume based demands, hydraulics more suitable for laminar flows and modelling fixture behaviour, extended water quality models (incl. temperature and Legionella) which can handle dispersion, stagnancy and transient behaviour. The interface should be able to show a three dimensional model with several fixture icons. And I would like to add, should be able to represent stochastic outputs. Walter addressed items 4, 5, 6, 8 and 9 in the table.
My conclusion about the webinar
It seems that PPM is a lot more complex than modelling the DWS. However, in 2020 this complexity is not insurmountable with fast computers and detailed insight into demands. Also, it seems that there are enough questions to answer related to (improved) design and operations and maintenance, especially related to water quality. It is interesting to note that no one addressed item 1 of the table. Whereas it is a key point, in relation to who would benefit (and thus pay) for research, see also https://www.kwrwater.nl/en/actueel/innovate-building-installations-but-also-assess-the-impact-on-the-whole-system/.
The next step will be that in the near future some more webinars will be organised on some specific aspects and going into a bit more detail. Hopefully by the end of the year it will be possible to also have a life event with discussions on how to take this forward.