Hello All,
In our Project we are installing a Water Treatment Plant where we are collecting grey water from sinks as well as capturing rain water and treating them and using them in the flushing of toilets in the building. The total daily capacity of the plant is 50 m³ i.e. 13.2 kGal.
I have gone through the Water Use Addition Reduction Guide and I am aware that these calculations should be used in the Alternative Compliance Path but I cannot understand how will we make the actual calculation. When I check leedonline forms for WEc1 and WEc3 I cannot find a place where I can subtract the adjusted total fixture water use annual volume performance case from Total calculated fixture water use annual volume baseline case. Where can I subtract the quantity of non-potable water use for flush fixtures? How can I do this calculation and where do I fill it in the leedonline form?
Pleas advice.
Michelle Rosenberger
PartnerArchEcology
522 thumbs up
June 14, 2014 - 5:20 pm
Hi Saud,
You take credit for it in WEcr2, but you do have to make 50% reduction in wastewater. We have a project with a cistern that is going to supply irrigation water and toilet flushing. WEcr3 is only about the total water reduction by virtue of low flow fixtures. But it does feed your WEcr2 calculation, so the lower the toilet fixtures the better. For toilet flushing, you would use WEcr2 and input your non-potable water volume. For WEcr1, should you be irrigating with it, you would also simply input the non-potable volume into the form.
Saud Abdul Rasheed
Sustainability/Energy Engineer, CEM, PMP, LEED AP BD+C, LEED AP O+M, Estidama PQP23 thumbs up
June 15, 2014 - 2:52 am
Dear Michelle,
1) What I understand is that we will get credit only in WEc2 then? The water savings from the treatment plant will be added and filled in WEc2 form.
But again wont this water add in the percentage of water savings in WEp1 and/or WEc3 as we are treating water (obviously giving us points in Innovative Wastewater Technologies) but at the same time we are using this water as non potable water for flushing (reducing potable water consumption in WEp1 and WEc3)?
2) I have a second question is how will I document the treated water annual voluem? 13.2 KGal is the volume of capacity of the plant. So in one day this can be the maximum water treated. How can I know how much water will be treated on a daily basis from flushes which may vary from day to day?
Michelle Rosenberger
PartnerArchEcology
522 thumbs up
June 15, 2014 - 2:57 pm
Hi Saud,
Yes, as I understand it credit for the reduction is only in WEcr2. In WEp1/c3, you are calculating "total" water reduction and not distinguishing between whether it is potable or not. LEED would still like to reduce demand first and foremost. That is why for example in WEcr1 about irrigation, you still have to make the 50% reduction in total water use even if you are using non-potable water to get the 4pts.
On the calculation, flushes don't vary because LEED gives you the daily use expectation. 3x each FTE user per day unless you have urinals, in which case it's 1x for men + 2x urinals + 3x for women. Visitors are also included of course. So fill out WEpr1/cr3 first with your low flow fixtures. The wastewater daily use volume from your toilets and urinals is going to feed into the WEcr2 form. If your plant capacity is greater than the wastewater volume you need on any given day, you would simply plug in the 100% wastewater value.
Michelle Robinson Schwarting
148 thumbs up
June 16, 2014 - 8:05 am
It's my understanding that you cannot take credit for the graywater/rainwater in WEp1 (per Addenda from 7/9/2010). However, per USGBC's Water Use Reduction Additional Guidance document (http://www.usgbc.org/resources/water-use-reduction-additional-guidance) you should be able to include it in WEc3 since you're reducing the amount of potable water needed for the regulated fixtures required to be included with this credit. And as Michelle Rosenberger said, you can also take credit under WEc2.
Once you determine how much graywater/rainwater you'll be able to use (i.e. what you'll have available based on the sink flow rates and the daily rainfall throughout the year combined with the plant capacity and cistern capacity) you subtract that total annual volume from the total annual volume consumed by the fixtures.
You might want to take a look at the LEED v2.2 Credit Form for where to subtract the volume (http://www.usgbc.org/sampleforms/v2) and either upload it or use it to check to see how the math is performed for your alternate compliance path. The v2.2 Form includes the basic math already to account for a given volume of graywater and rainwater use. Just make sure you're using the correct flowrates and durations for the baseline case (and remove the janitor sink) per v2009, since some of them have changed. (And if you're using metering faucets, it'll be a bit of a hassle to convert them to the v2.2 form...)
You also might find more info on LEEDuser under the WEc3 credit since that's where you should be allowed to take credit for the rainwater as well. (There may be some guidance there about whether or not you'll need to do calculations for the full year on a daily basis with actual historical rainfall data since some days you'll get more rain than others or if you can make some assumptions/generalizations...)
Saud Abdul Rasheed
Sustainability/Energy Engineer, CEM, PMP, LEED AP BD+C, LEED AP O+M, Estidama PQP23 thumbs up
June 16, 2014 - 8:38 am
Michelle Rosenberger,
Michelle Robinson,
Thank you so much for your replies and detailed explanations. I did all the calculation for the flow fixtures and flushes. I still cannot figure how to make calculations for the treatment plant.
Also there is still one problem. In the LEED BD+C CS 2009 forms I cannot find any table or calculation for non potable water in WEc3. For WEc2 there is a place to add non potable water but for WEc3 there is only the calculation tables for flows and flushes. I want to use this treated grey water and include it in the WEc3 but I cannot find where to do this math in the form?