The topic for value engineering this quarter is Plumbing. Division 22 does not get a lot of attention when it comes to preconstruction value engineering, but there is still some value to be found and squeezed out of the trade. The following article will explain some of the questions we ask ourselves on this topic. As with past articles, I will try to avoid basic questions regarding the price and quality of the fixtures and finishes.

If extra heavy weight cast iron is specified for underground plumbing, can service weight be used instead?

Opinion on this one differs, even internally to Monadnock, but officially and notwithstanding specific site conditions that might make it inadvisable, we accept service weight in lieu of extra heavy cast iron for underground plumbing. If extra heavy cast iron is specified (and it often is) and the underground piping scope is significant, savings can sometimes be in the hundreds of thousands of dollars.

Are bathrooms back-to-back, or as much so as they can practically be?

This one is a classic. Just when we think this one no longer needs to be explained to designers, another plan set will drop on one of our desks where the architect clearly ignored this fundamental rule of laying out apartments. When the bathrooms are “back-to-back” it means they can conveniently share cast iron risers and starter fittings, saving cost by avoiding redundant material and labor. 

It also means it will be easier for the bathrooms to share a toilet exhaust riser. The mirrored bathrooms are also likely to result in back-to-back kitchens (allowing apartment to share kitchen exhausts along with other efficiencies).

Sometimes the designers will heed the letter of the law and not the spirit, making the bathrooms physically adjoining without laying out so that they can take advantage of this with shared cast iron.

How is domestic hot water being made and can it be more efficient?

One of the first things I look at in an MEP set is the method of domestic hot water production. Like most of these questions, opinion differs. Furthermore, we are also often at the mercy of the preferences and superstitions of the low qualified bidder. However, we have found success with the following line of reasoning. (1) All else equal, increasing the capacity of a piece of equipment is typically less expensive than adding another piece of equipment and splitting the capacities. (2) All else equal, fewer pieces of equipment is less expensive than more, especially if it is equipment that requires connections from multiple trades. In this line of reasoning, if a project already has hydronic space heating, we will look to see if savings can be achieved by generating domestic hot water through heat exchangers (HHW-to-DHW) rather than separate pieces of direct-fired domestic hot water equipment. Likewise in reverse: if there is no hydronic space heating as part of the project, we will make sure that the domestic hot water heaters are the direct-fired, potable-rated type (i.e., not space-heating boilers piped to HHW-to-DHW exchangers).

Related to the last topic, can Electric Heat Pump Domestic Hot Water be avoided?

Most of us have never seen this setup, but it is coming. Whatever you think of the practicality of this goal, New York City is pushing more and more for fully electric buildings. Developers are winning RFPs on the basis of this promise and codes are adapting. The trickiest part of designing and building an all-electric project is domestic hot water. Unfortunately, the technology we have seen for the purpose (electric heat pump domestic water heaters[1]) is absurdly expensive. As best we can tell, we typically pay between $20 and $30 per mbtu for our high efficiency, gas-fired hot water heaters. Although $/mbtu is not the best metric (since some buildings might have heaters sized to meet peek demand while others might instead have storage tanks sized to meet peek demand and significantly lower capacity heaters), it is still significant that the quotes we have so far seen for electric heat pump domestic hot water heaters have been over $300 per mbtu. The relative cost of installation and gas piping vs electrical work remains to be seen. Our buildings’ average mbtu seems to be around 10,000, making the ballpark upgrade cost for this feature somewhere around a quarter million dollars in equipment cost..

If trap primers are specified, can they be eliminated?

Fancy engineers, in their profligacy, seem to also have a dim view of building superintendent’s ability to prime a trap. We will often see automatic trap primers specified for all floor drains in a lurking drawing note. Nevermind that the engineer did not bother to show the domestic water connection for this automatic primer on the riser diagram, they want it! But we rarely provide them as the added expense of the added piping (aside from the fixture) is rarely justified for the benefit.

Can fixtures be used to double as air vents?

Although this may be considered a constructability or final building quality issue, one thing we look for (or should look for more in the future) while we are value engineering is whether the fixtures at the top level of the building can be used as automatic air vents. This can be accomplished by moving the hot water or hot water return distribution below the level of the highest fixtures. (Designers will typically place this at the top floor without our intervention.) Despite all the design measures to avoid it, air pockets inevitably develop in the domestic water piping and impede the flow of water especially during system start-ups and repairs. With the top floor fixtures acting as air vents, we are able to minimize the air more than we otherwise could and resolve so-called “balancing” issues (we find that these air pockets noticeably delay the onset of hot water at far-away fixtures) before they arise.

Are all the piping specifications reasonable?

An exhaustive list of all the unreasonable plumbing specifications we have encountered is not feasible here, but here are some of the classics you might find lurking in a specification book.

• Extra heavy cast iron for underground piping. (Covered above.)

• 100% Heavy Duty Couplings for No-Hub Piping

• Seismic Hanging. (There may be some projects where this is actually required but for the most part it’s not.)

• 100% Brazing for Copper Pipe. (I.e., no soldering.)

• Press fittings prohibited. (We typically allow plumbers to use their preference.)

If each set of domestic risers has it’s own hot water recirculation line, can these instead be combined into one?

Besides choosing pressure zones vs. local PRVs or the location of lateral distribution, the biggest decision that comes up early on regarding the domestic distribution system is how to handle the hot water recirculation or return risers. We often see an individual return riser at each chase and we also often see a combined return riser for the whole building. Since our building are predominantly vertical, we will typically recommend combining the returns into one riser if we see a plan set where it has been drawn the other way around.  

Can the stormwater detention tank be moved outside the building?

There is likely little difference, at least little consistent difference, in the cost between a precast and a cast-in-place detention tank in our buildings. However, the cost of waterproofing these tanks (which we only do for interior tanks) is significant. It seems to be consistently over $20/SF—depending on the specification for the waterproofing and the wage requirements of the project. Aside from the value engineered savings that may be found in eliminating this scope, moving the tanks to the exterior and eliminating that work means one less dangerous and confined space activity that must be performed.

Have back-outlet fixtures been appropriately specified?

Although this is more of a constructability (vs value engineering) item, it can lead to unnecessary cost as well. For plank projects where sleeves, depressions, and cores are not as easy on a cast-in-place structure, we always look to make sure that toilet and bathtubs are specified as back outlet. Otherwise too much work has to be performed in the field to install each of these fixtures, generating unnecessary cost and brain damage.

Are domestic valve quantities and location reasonable?

What we typically build is a domestic water distribution system with valves located on one (or a couple) floors in a publicly accessible area. This results in a single distribution floor on some level where the super can access the valves in the corridor. Individual apartments cannot be shut off without shutting down a whole line, but this is the tradeoff for not having to spend a lot more money up front on valves and piping (and maybe winding up with some difficult to reach valves).

Does the client really want their refuse room hose bibs and floor drains?

Some fixtures shown on drawings are simply not required. For example, not all of our jobs have hose bibbs and floor drains in the typical floor refuse rooms. Many owners don’t realize this is atypical if their typical floors also have a janitor’s closet or if there are generally enough janitors closets, so if these are shown on drawing sets they can often be eliminated. Keep in mind that providing in on just some floors (like every other) will not yield full savings since the risers will still be required.

[1] Electric resistant heaters for domestic hot waters have been a non-starter due to operating costs.

[2] Sometimes a riser diagram will look like this and the engineer is only referring to speedy valves with the valve symbol. But sometimes they actually mean shutoff valves at the apartment or riser location (i.e., not at the fixture).