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Building codes and 1.6 or 1.28 gallon/flush toilets

Posted by annkathryn (My Page) on
Thu, May 31, 12 at 20:49

I just received comments back from my city regarding my plans and saw that the toilets need to be 1.28 gallon/flush. I was planning on purchasing a dual flush toilet that's 0.90 and 1.60. Has anyone else faced the same requirements and been successful in using a dual flush?

My city's Design Guidelines aren't currently online so I can't get any further information at the moment.

Follow-Up Postings:

RE: Building codes and 1.6 or 1.28 gallon/flush toilets

Plumbing codes and the bureaucrats writing them, are often out-of-touch with the real world.

How old is your home? What size plumbing line is in place for your current WC? That is important and may resolve everyones issue. Old code was 4" waste line for a WC. 4" is too large for 1.28 gallon flush because the flush will not concentrate sufficiently to wash solids through. Then a clog. 1.28 gallon needs a 3" waste line.

Seems to me your dual flush would work for either. Ask your plumber.

RE: Building codes and 1.6 or 1.28 gallon/flush toilets

Thanks for your response.

I just spoke with a city building inspector who said the dual flush would be fine. The house was built in 1949, I have no idea what the current waste line is but he said the code is for 3".

RE: Building codes and 1.6 or 1.28 gallon/flush toilets

I'm glad you have approval for the dual flush WC. Unless your home has been replumbed, you most likely have 4" cast iron waste lines. A new 1.28 gallon WC would have been a major problem.

This is where building departments, inspectors and codes fail existing homeowners whose homes were constructed according to codes in effect at the time. They need to be advised appropriately and generally aren't. Good luck with your project.

RE: Building codes and 1.6 or 1.28 gallon/flush toilets

The dual flush toilet can be deemed equivilant to a 1.28 gallon model where the average volume of 1 full flush and 2 partial flushes equates to 1.28 gallons or less. You can verify all toilet models at; in addition this site will reveal the flushing performance of the toilets.

While it is true that oversized sewer lines can be the cause of blockages, this is RARELY a problem in homes. The water from baths and showers is almost always sufficient to push the solid waste down the line.

Here is a link that might be useful: Maximum Performance Toilet Tests

RE: Building codes and 1.6 or 1.28 gallon/flush toilets

Vincent the average gallon calculation makes sense to me. I'm happy to be saving water.

I just took delivery of two dual flush toilets, both Totos. One is wall-mounted for a very small bathroom, and the other is a Toto Aquia. It will be another couple of months before they're installed. I'll try to come back with a review of both.

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