Feeding the Building Plumbing Microbiome: The Importance of Synthetic Polymeric Materials for Biofilm Formation and Management

Round 1

Reviewer 1 Report

The manuscript written by Neu and Hammes provides a review of the role of the building plumbing system in contributing to bacterial growth, specifically emphasizing the role of plumbing materials. The manuscript is well-written, summarizes a thorough review of the literature, and provides a novel review of a topic that has not been previously explored in the literature. I have only minor comments regarding a few points that should be elaborated upon in more detail to strengthen the manuscript. 

Most notably, the manuscript would benefit from expanding on the topic of nutrient-based selection. The occurrence of nutrient-based selection is fundamental to understanding the role of plumbing materials in shaping the microbiome, yet it is not well explored in this manuscript. What is currently known about this subject? To what extent have various plumbing materials been documented to select from certain pathogens or certain microbial communities? What is known about the cause of this selection and what makes certain microbes better suited to establish themselves in that niche environment?

On line 158, the authors state that a variety of parameters can be managed to control building plumbing microbiology. Of course, there are a long list of potential trade-offs that should be considered when manipulating these parameters (i.e. energy efficiency, cost, increased stagnation vs. increased flowrate when manipulating the size of pipe materials, etc.) that should be very briefly mentioned. 

Finally, what are the long-term implications of plumbing materials on microbial growth in building plumbing? The manuscript and model largely focus on the changes that happen upon commissioning of new plumbing systems. To what extent are materials expected to continue to influence microbial communities over time?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript contains good review information regarding the impact of pipe materials on plumbing microbiome. 

A reviewer has some suggestions for the manuscript. 

1) The paper needs to include some discussion and review summary information for organic matter levels in finished/treated water.

Although carbon migration from pipe materials may be important, unremoved organic matter from a DWTP will enter the DWDS and will be significant compared to carbon leaching from different pipe materials.

I think authors can update the manuscript with some information related to organic matter levels in DWDS and their impacts on biofilm in building plumbing.

2) what is a common residual disinfectant level and its impact on biofilm formation in building plumbing systems? 

3) how long carbon can migrate from polymeric materials? Authors cited most of their papers but did not discuss how long carbon can migrate from pipe materials.

4) many referred regulatory information is mostly for European countries. It will be good to have some information for US. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf