Shower - 2 inch transiiton to 1 1/2 inch and venting

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Turnerover32

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Hi


I have a few questions about replacing an existing bathtub with a shower as we remodel our bathroom,

The existing tub on our upper floor was plumbed with a 1.5 inch p-trap and then a horizontal run of about 9 feet before it heads vertically downwards towards the basement between all the walls. My understanding is that code calls for 2 inch drain pipe for a shower. My question is somewhere along the line (I can rip up the subfloor) I need to transition form the new 2 inch drain to the 1.5 inch line and what would be the best place to place this reducer to minimize the speed at which water can flow. It could be right at point the drain meets the the p-trap where I could reduce to 1.5 inch p-trap or I could put in a 2 inch p-trap and 2 inch line and then transition at the point the horizontal drain line connects to the 1.5 inch vertical drain line between the walls headed to the basement. I am thinking the second option would be better?


My second question I son venting- the existing tub never drained very fast. The current vent is about 52 inches form the existing p-trap. I have looked at code on the web and it varies by jurisdiction with it being with 5 feet in some and within 3.5 feet. My question is if I move the vent closer than the existing 52 inches could I increase the rate at which the water drains. If I actually left the first vent in place and added a second vent that was closer could this cause a problem?

Any advice would be appreciated
 

NHmaster

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Never ever can you reduce the size of a drain. You must take it all the way back to the larger pipe.
 

Geniescience

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Many think a 2" trap can be reduced to a 1.5." pipe after the trap: not true; not good; no.
"Do not decrease any drain line in the direction of flow."
The trap size has to be the same as the drain size.
This is very serious, not to be disregarded.
Ask a Master Plumber if you need to hear it again.


The OP is in Canada. afaik each province has its own code, and they all allow 1.5" drains. Everyone says so, but I've never seen it in writing. Check with a Master Plumber. Any Master Plumber. They are professionals who do not lie. They know 100% for certain what is required and they tell you the truth, when it concerns their expertise; also you do not have to hire them first before they answer questions about their area of expertise. Each Master Plumber will give you the same answer as the previous one and the next one.


Use a 1.5" trap if the drain line is to going to be 1.5" diameter.
You may wonder why you see on the internet that showers need 2" ...
I feel that this forum is the right place for this discussion.

It find the 2" diameter requirement for showers to be overkill.

!
I'm surprised that after many years of searching, I've never seen an internet comment from an experienced Master Plumber telling me how Code changed over the years.
!

I'm 100% certain that a 1.5" drain line used to be Code everywhere, for showers. I'd like to know what discussion went into voting for the new size, 2" diameter.

(?)
Here is a link showing 1.5" is OK in NY.
http://publicecodes.citation.com/st/ny/st/b900v07/st_ny_st_b900v07_7_sec009.htm

and here is the thread that raised this : https://terrylove.com/forums/showthread.php?t=29678


Imagine all the people who have been forced to do a lot of extra work for no reason !! When a 1.5" drain already plumbed could have been used, they ripped it all out and put a 2" drain in.

I'm not a plumber. Since this is a discussion forum, I'm posting this here as part of a *discussion*; everything I have written here concurs with previous posts.

Code has changed over the years and will continue to change in the future.
I'd like to think I'm helping to air out the issues which leads later to clearing up confusion about 2" shower drains.

Anyone can glue a reducer into a 2" opening, so the fixture itself takes a 1.5" drain.
Shower drains can be made with a 1.5" opening.
The reason you may not see this is stores (shower drains with 1.5" openings) is simple: you glue in a reducer and you are done; no need for the manufacturer to make two types.

Hope this helps.
 

Gary Swart

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I can't quote chapter and verse of codes, but it is my understanding that the 2" shower drain requirement is to provide a measure of protection from a clogged drain flooring the room. A tub has a larger storage capacity for backed up drains so only require a 1-1/2" drain. It should be common sense that reducing a drain creates a very real place for a clog to occur and certainly makes this a very reasonable code requirement. On a related subject, new washing machines dump water much faster than old machines and therefore a 2" drain is required.
 

Kingsotall

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They might "dump" them faster but then again front loads use WAYYY less water than they used to so who knows.
 

Doherty Plumbing

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Many think a 2" trap can be reduced to a 1.5." pipe after the trap: not true; not good; no.
"Do not decrease any drain line in the direction of flow."
The trap size has to be the same as the drain size.
This is very serious, not to be disregarded.
Ask a Master Plumber if you need to hear it again.


The OP is in Canada. afaik each province has its own code, and they all allow 1.5" drains. Everyone says so, but I've never seen it in writing. Check with a Master Plumber. Any Master Plumber. They are professionals who do not lie. They know 100% for certain what is required and they tell you the truth, when it concerns their expertise; also you do not have to hire them first before they answer questions about their area of expertise. Each Master Plumber will give you the same answer as the previous one and the next one.


Use a 1.5" trap if the drain line is to going to be 1.5" diameter.
You may wonder why you see on the internet that showers need 2" ...
I feel that this forum is the right place for this discussion.

It find the 2" diameter requirement for showers to be overkill.

!
I'm surprised that after many years of searching, I've never seen an internet comment from an experienced Master Plumber telling me how Code changed over the years.
!

I'm 100% certain that a 1.5" drain line used to be Code everywhere, for showers. I'd like to know what discussion went into voting for the new size, 2" diameter.

(?)
Here is a link showing 1.5" is OK in NY.
http://publicecodes.citation.com/st/ny/st/b900v07/st_ny_st_b900v07_7_sec009.htm

and here is the thread that raised this : https://terrylove.com/forums/showthread.php?t=29678


Imagine all the people who have been forced to do a lot of extra work for no reason !! When a 1.5" drain already plumbed could have been used, they ripped it all out and put a 2" drain in.

I'm not a plumber. Since this is a discussion forum, I'm posting this here as part of a *discussion*; everything I have written here concurs with previous posts.

Code has changed over the years and will continue to change in the future.
I'd like to think I'm helping to air out the issues which leads later to clearing up confusion about 2" shower drains.

Anyone can glue a reducer into a 2" opening, so the fixture itself takes a 1.5" drain.
Shower drains can be made with a 1.5" opening.
The reason you may not see this is stores (shower drains with 1.5" openings) is simple: you glue in a reducer and you are done; no need for the manufacturer to make two types.

Hope this helps.

Up here in Canada basically every province uses the National Plumbing Code which is basically a rewritten version of the BC Plumbing Code.

We are more then allowed to use a 1.5" drain for a shower. In fact it's the norm. But the 1.5" drain has limitations on where and when it can be used. But for a residential, light commercial, it's perfectly acceptable.

I can't quote chapter and verse of codes, but it is my understanding that the 2" shower drain requirement is to provide a measure of protection from a clogged drain flooring the room. A tub has a larger storage capacity for backed up drains so only require a 1-1/2" drain. It should be common sense that reducing a drain creates a very real place for a clog to occur and certainly makes this a very reasonable code requirement. On a related subject, new washing machines dump water much faster than old machines and therefore a 2" drain is required.

This argument to me really doesn't make much sense to me.

If you have a sewer back up it doesn't really matter what size your shower drain lines are. If they're the lowest point they're going to flood. And if your shower drain is the only thing clogged then this isn't really a big issue because you can just turn your shower off to prevent flooding.

Also showers put out less water so you'd want smaller pipe diameter to increase the amount of buoyancy the water has to carry away material like hair etc. Going to a larger drain size isn't always a better choice.

To me it makes more sense to have a 2" drain on a tub an an 1.5" drain on the shower. Mind you I don't plumbing in my bathtubs with 2" drains because they don't need them.

But I'm up in Canada and I don't know what your code says about what's required but I know what works :)
 

NHmaster

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The OP has apparently decided to.. And will undoubtedly go with the drain reduction.
 

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