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Flush is slow, but 5 gallons of hot water works perfectly

GDH2's picture

Problem: 2 upstairs toilets flush slowly.Time after pushing handle until water at bottom (i.e., fully flushed) takes 10 seconds in one and 20 seconds (or more) in the other. 

Layout: 2 bathrooms on second floor that share a wall, each has 1 toilet, 1 sink, and a shower. I think the downpipe is probably under 1 shower, 4' from the worst toilet, 6' from the other toilet, about 6 and 8' for the sinks, and 9-10' for the tub. House built 1985, PVC, I'm the original owner.)

Steps taken so far:

  1. Pour 5-6 gallons of hot & soapy water into both toilets. Flush action is fast and perfect. (2 Tbsp dishwashing soap, pouring from about 3' high, pouring fast)
  2. Stick a wire into the holes under the rim. Zero signs of corrosion, no resistence, no debris. Whenever I fulsh, they seem to all put out spiraling water streams. 
  3. Tank flapper works properly (trap door opens fully and stays verticle until water has dumped out)
  4. I've augered both with both a toilet auger (4' body w/ rubber end) and a drain auger (25', round) - I got almost no debris (a few tablespoons at most from both)
  5. I ran all the taps full simultaneously - both sinks, both showers, and a toilet. Everything drained properly, no slowing down or sink or tub filleing.
  6. No unusual noises.  Several sources suggested a clogged vent would cause the sinks to gurgle.

What should I do next?

  1. Dump Zep Drain Care into both sinks and let it soak overnight?
  2. Remove a sink trap to prove that the problem is NOT bad venting? (Would this be a valid test? The sink trap is higher than the toilet drain...)
  3. Remove the slower of the two toilets and probe directly into the drain pipes?
  4. Climb up on the roof? (The eave is 30' above ground, so itr's not trivial. I also have access to the vent pipe in the attic.)

 I try to be concise, but I am too ignorant to know what is or isn't important. I'm always gald to give additional feedback or answer questions. 

THANK YOU VERY, VERY MUCH!

Doug The Wood Loon in Acton, MA

Lots of tools that need to be used more! I ask to learn how and I am always grateful for that help.

When you push the flush (post #215210, reply #1 of 8)

When you push the flush handle it starts water flowing from the tank.  The flush won't finish until the water stops flowing.  How long this takes depends on the size of the tank and the design of the flush valve.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

DanH, thanks. I have 3 (post #215210, reply #2 of 8)

DanH, thanks.

I have 3 identical toilets. I am using "seconds to end flush" as a yardstick.

  • Downstairs toilet = 6 seconds. It's perfectly typical. 
  • 10 seconds is almost OK - sometimes it needs be flushed twice, maybe 20%, and the last of the toilet paper doesn't get through the siphon about 50% of the time. 
  • 20 seconds or longer (sometimes it never drains completely) = a real problem!

I hope this helps. 

Doug The Wood Loon in Acton, MA

Lots of tools that need to be used more! I ask to learn how and I am always grateful for that help.

What happens to the water (post #215210, reply #5 of 8)

What happens to the water level when you flush?  If it rises very briefly at the start and then dips below the starting depth for most of the flush then you don't have a clog -- likely there is something wrong with the flush valve, or the holes around the rim are clogged.

If the water level rises stays high for the duration you have a clogged drain.  A clogged vent will be somewhere in-between.

(And if you can get a decent flush by pouring a bucket of water into the toilet then there is no clog.)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I had this exact problem. (post #215210, reply #3 of 8)

It turned out that after +20 years, some of the drain holes in the tank were plugged by debris, which prolonged the time necessary for the tank to drain to the point where a complete flush did not take place. 

I fixed it by replacing the commode with the American Standard 18 ping pong ball model. This doesn't flush, it INHALES. Highly reccommended. 

Good luck. 

I'm not really sure I have (post #215210, reply #4 of 8)

I'm not really sure I have ever cared how LONG a toilet flushes....much more concerned about WHAT it flushes.  Block the shower drains with a plastic bag.  Do the same with the sink drains and the overflow hole in the sinks  then do your bucket pour and see what happens.  I suspect you have a clogged vent and by blocking of other possible sources of air what you should see is pouring water in toilet A sucks the water out of toilet B as it searchs for vent air. If you have shower/tub combinations block the overflow in the tub as well.

Toilets. (post #215210, reply #6 of 8)

If these are American Standard low flow toilets about 20 years old, replace them. That's how they work.

Each tank holds approx. 4 gallons (post #215210, reply #7 of 8)

mike mahan wrote:

If these are American Standard low flow toilets about 20 years old, replace them. That's how they work.

Mike - You made to realize I've never measured the quantity of water, although I am sure it's "full sized." But maybe... 

  • 17" W x 7" D x water inside is 10" high (although the tank is about 14" W at bottom)
  • 15.5 * 7 * 10 = 4.4 gallons

I could not find any "model" designation. I assume the casting numbers in the tank refer to the tank itself.

Doug The Wood Loon in Acton, MA

Lots of tools that need to be used more! I ask to learn how and I am always grateful for that help.

I've solved that problem in (post #215210, reply #8 of 8)

I've solved that problem in more than one toilet with some muratic acid, a toilet mop (not brush) and a piece of bent coat hanger.  The holes under the rim become encrusted with scale and don't alow adequate water to flow down the sides to give a good flush. Pour a cup of acid into the tank and another cup into the bowl. Use the Jony mop dipped into the bowl and mopped under the rim to break down the crust. Do it for 5 minutes or so then flush to force tank water through the rim holes. Then, bend your piece of coat hanger wire so you can clean the holes under the rim from on top. The whole thing will take 10 minutes and your toilet will flush like new. 

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.