3" Or 4" ?

protechplumbing

It's to vary depending on the fill/flush valve design but....yes that black tube is what refills the bowl.

And Ron is correct about excessive pitch being a non-issue.

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BCConstruction

Cheers Ron thats good to know. I was never 100% sure if that was the reason.

BCConstruction

Thanks Protech. As of yet i have never seen a issue with to much slope on a toilet over here so perhaps the combination of Siphon jetted and 3" soil pipe the flow rates are a lot higher and faster to clear the solids. These new 3litre flush cisterns and non water saving pans aint a good combo either in the UK. They are really ment to be used with a water saving pan thats design for a 2 stage flush cistern.

Right im off to bed. Thanks for the info guys.

Plumbus

I know that it sounds counterintuitive to say that a 3" line would be more appropriate then a 4". There was a time when I would have argued for the larger line. When the law requiring toilets to flush using no more then 1.6 GPF took effect in the mid '90's, plumbers started noticing stoppages on sewer lines which had previously given satisfactory service. While the general public was complaining about toilets that wouldn't flush, plumbers were trying to fathom this other consequence of a well intentioned law designed to save potable water.
The problem is called inadequate line carry. In other words, the new toilets might evacuate the solids from the bowl, but the amount of water used is so small that it can only carry the solids a fraction of the distance a 5 gallon or even 3.5 gallon flush toilet did. One of the ways to improve line carry is to decrease the diameter of the discharge pipe. This is especially important when dealing with a single rather then a battery of toilets. Though other fixtures also contribute to flow, they, too, have built in restrictions on their gallons per minute. When you add in the fact that this is a guest house, with intermittent usage, the possibilities of stoppages can be magnified. This is due to solids falling out of suspension, partially drying because of sporadic use and creating damns which can trap other solids. Add to this the strong possibility that the toilet used in the guest house will be a 1.3 GPH unit (the about to be enforced government standard), thus decreasing flow even more.
A 3" pipe is no guarantee that a stoppage won't occur, but, with 3" there will be better line carry and wall scouring then with 4". I say this with the conviction of one who knows he will be held accountable if there is a problem down the line.

Plumbus

I posed this question to John Koeller, the engineer who tests toilet performance for the CEC and his response (which for the life of me, I can't find) was that they are currently testing line carry and pipe sizing. He says the preliminary results show a better line carry for 3". When they are done with their testing we will have a definitive answer to this question (and some new tables in the model codes).

ct plumber

[quote=Celtic;772777]Why?

I generally see 4" cast with lead elbows all over.[/qu

I dont know anyone who uses lead bends anymore,as far as the toilet,if you ever look at the opening on the bottom,its only about 2 1/2.You can put 5 toilets on a 3'' line these days,plumbers go by DFU.Thats how lines are sized by the code.

KillerToiletSpider

Not in Chicago.

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A flush is better than a full house.

Ron The Plumber

Not in Oregon

protechplumbing

or Florida

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Celtic

Neither do I....but that doesn't mean the lead bends aren't there.

For clarity, I do a lot of old work.

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ct plumber

Sounds like some other states are behind the times?

protechplumbing

Back when 4" lead arms were the norm, a wc would flush 7 gallons or more. That's more than 4 times what they flush now. More water back then, bigger pipe back then. Less water now, smaller pipe now.

The problems start when people install a 1.28 gpf wc on and old rust scale encrusted 4” line. A service plumber’s wet dream

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Ron The Plumber

So do I

ARealplumber

I know you do. All us repair guys have seen our fair share of lead.

Ron The Plumber

When you going to become a member on www.plumbingzone.com

Pipe Wrench

2 Toliets are allowed on a 3" soil stack SFH's. Closet bends are 3" x 4". However code reuires that the flanged itself, for effectiveness, not be less then 4 1/2", beveled on the top. Now try and get 4" pipe in a 2x4 wall, gl , cause most SFH's are 2x4 Walls. As far as theory, toilets are designed S-traps, which by code are illegal for any other plumbing fixture, depending on state. IE freeze areas, where you would bring a waste line up threw the bottom of a cabinet, and trap the fixture, not run the waste or water line up in the exterior wall. In SFH's there were never be enough Negitive pressure to siphon P-traps dry allowing sewer gas to engulf a home.