Low water consumption and plugged drain pipes go hand-in-hand?

[Rerod]

I am reading in more than one place that this is the case.

I do maintenance in a building that was built in 1912 and we are in the process of switching toilet diaphragms to 1.6 gallons per flush when the old 2.4 diaphragms fail. I’m trying to warn management that this is a bad decision but it’s falling on deaf ears. Are my concerns warranted? And just wondering, how are new building designs different to accommodate for low water consumption fixtures?

Thanks.

 

[John Gayewski]

The toilets use less water, but it gets delivered faster into the piping. This is how a pressure assist toilet can use 1 gallon per flush. It throws the one gallon down the drain faster. Over a long run of pipe with fittings I don't think this actually helps that much. I don't see 1 gallon of water taking solids safely through 300ft of cast iron piping, but what do I know I'm just a dumb plumber. I don't study this in a lab.


I've always been a believer in using minimum pipe size for drainage. Not a fan of wet vents or combination systems. Even more so, with less water being used.

An older system in my opinion does need more water to run, but this depends on the piping and how long and horizontal the runs of drainage piping are, what materials are in use, and their condition.

I am pretty sure over the next 1 to 3 code cycles the pipe sizes will change for drainage and/or water.

 

[Sponsor]

 

[Jeff H Young]

The toilets use less water, but it gets delivered faster into the piping. This is how a pressure assist toilet can use 1 gallon per flush. It throws the one gallon down the drain faster. Over a long run of pipe with fittings I don't think this actually helps that much. I don't see 1 gallon of water taking solids safely through 300ft of cast iron piping, but what do I know I'm just a dumb plumber. I don't study this in a lab.


I've always been a believer in using minimum pipe size for drainage. Not a fan of wet vents or combination systems. Even more so, with less water being used.

An older system in my opinion does need more water to run, but this depends on the piping and how long and horizontal the runs of drainage piping are, what materials are in use, and their condition.

I am pretty sure over the next 1 to 3 code cycles the pipe sizes will change for drainage and/or water.

Totally agree with response. going oversize I'm not so sure helps any and can harm . I cant confirm or not on say whether 3 or 4 waste carrying W/c waste will perform better . on old systems 50 to 100 year old My gut says more water is better. A lot of old buildings were not plumbed that good either.
I'm not aware of problems, changes that should be made to pipe sizing , especially on residential it seems plenty big enough on water and waste.
perhaps a few dollars saved by allowing smaller piping or some corner cutting to save on construction costs.

 

[Reach4]

I am pretty sure over the next 1 to 3 code cycles the pipe sizes will change for drainage and/or water.

Which way do you predict -- larger or smaller required/permitted?

 

[Jeff H Young]

larger water , smaller waste? to allow better blasting effect a guess .
In California with all this draught and water prices I'm thinking we are going to continue in water saving technology.
but code changes in piping I'm unaware of

 

[John Gayewski]

Things like shower waste pipe will probably go down to 1.5". I don't see how a water closet could get smaller than 3"due to the solids. Washing machines should be able to go to 1.5" (although not entirely sure about that).

Water supply piping has already been getting smaller with the explosion of pex piping. Pex B with the tiny fittings is about the same as running 3/8" copper.

I think most of the changes in the water supply will be on figuring the loads and the tables used will change branch and main water line sizing. The complexity comes with different types of pipe and systems of fittings. The code won't change enough to risk undersizing nor will it get minut enough to size things using all of the different systems, so much will remain unchanged.

The NEC has different standards for remodel and new construction which I always thought was a good idea. Who knows if plumbing (upc) will get into the weeds on this. I'm gonna doubt it.

 

[Jadnashua]

In the real world, on a long horizontal (minimum code slope) run, the wastes don't make it all the way to the sewer on the first flush. This isn't usually a big problem as later on, someone will run their WM, or take a shower where a much larger volume of water will finish the task. What IS an issue is where the original line is not installed properly (i.e., bad slope, flat, back slope, or bad joints that catch things).

With today's front-loading WM, they spin so fast that a typical 1.5" drain line will back up. On a shower, if everything is good, 1.5" is probably okay, but stand on the drain for a bit, let some water accumulate, or have an issue in the drain, then you'll be glad you have a larger pipe!