View Full Version : Weak flush

09-08-2012, 02:36 PM
I need some advice.

A toilet in our half bath has a weak flush. We've snaked the toilet (nothing). Removed the toilet and snaked the line (nothing). Still a weak flush. What other troubleshooting steps could I take?

PS. We also used the garden hose to run water down the line. No issues.

09-08-2012, 03:18 PM
Did it always do this, or have things changed recently? If it's always been marginal...it may be time for a new toilet!

There are things that can get caught in the trap of a toilet that a snake will just pass by, so there could be a comb, pencil, pen, toy,etc. trapped in there. If the water level is not proper, it won't flush well. If it has clogged rim holes, it won't clean the bowl or flush properly (a metal coat hanger can ream them out). If the siphon jet (if it has one, not all do) is clogged, it won't flush well. So, it's hard to say without being there.

If you hold the handle down to empty the tank, does it flush any better? Have you changed the flapper valve recently? It may not be the right one, and is closing too soon.

09-08-2012, 03:27 PM
Also, give us a little more color on what you mean by "weak flush". Stuff doesn't go down? Not a lot of water comes in the bowl? A lot of water comes in but it doesn't go anywhere, or comes in slowly?

09-08-2012, 06:25 PM
@jadnashua - It hasn't always been this way. In fact, it's been difficult to figure out a pattern to this issue. It's been happening for a while. After talking with my wife about this, we think that this happens almost always when it rains heavily. We are at the end of a dead end street with a sharp drop off just beyond our house.

@wjcandee - For us "weak flush" means that it goes down slowly and stuff goes down but only after a few flushes. Water fills the bowl to the rim and then goes down to about half.

Update: The rain stopped and its flushing better, but not back to normal.

09-08-2012, 07:11 PM
Vent issue?

09-08-2012, 07:54 PM
A toilet will flush without a vent...now, it may create problems elsewhere in the system.

Is this toilet the lowest in the house? How high is it verses where the sewer line exits the house?

If the sewer line is full, or slow moving, you may not notice problems from higher up drains until the problem becomes worse - you can't flush into a full, or nearly full drain line. Tree roots, collapsed pipe, a belly (i.e., a dip) in the line can have standing water or significant restrictions and affect things.

Is it better or worse when say the washing machine is draining, or you're emptying the tub, or several people may be taking a shower?

Homeowner type snakes and even incorrectly used professional ones can appear to go through but not actually clean the pipe well. Sometimes, you need to use a camera in the line to see if there's any issues.

09-08-2012, 08:25 PM

A toilet bowl is nothing more than a glorified siphon.

With a siphon hose, you suck on the end of the hose to fill it with water (or any liquid) and as long as the outlet end of the hose is at a lower elevation than the level of liquid in the container you're siphoning from, the laws of physics take over and the siphon keeps going until something stops it.

It's exactly the same thing With a toilet bowl, 'cept you don't suck on the outlet end of the toilet.

Instead, the toilet tank dumps enough water into the toilet bowl fast enough that the volume of water overflowing the weir inside the toilet bowl and entering the discharge channel is sufficient to fill that discharge channel competely with water.

And, once that happens, them same laws of physics take over and turn that discharge channel into a powerful 2 inch diameter siphon hose, which sucks up the water in the toilet bowl.

Provided nothing interferes with that process, then you have Sir Isaac Newton's personal guarantee of a successful flush every time.

But, as Jadnashua says, there's lots of things that can interfere with the process:

- not enough water entering the bowl or not entering fast enough

- not enough room in your toilet's drain pipe to accomodate the water.

The way to tell if the problem is upstream or downstream of the water level in the toilet bowl is to pour a 5 gallon pail of water as quickly as you can (without spilling any water on the floor) and seeing if the bowl flushes properly then.

If it does, then the problem is upstream of the water level in the toilet bowl. Check that the tank flapper is opening fully, that the holes under the rim of the bowl are open and flowing, that the jet hole at the bottom of the bowl (if you have one) is open and flowing.

If it doesn't, then the problem is downstream of the water level in the toilet bowl. Maybe there's something caught in the toilet discharge channel, maybe the drain line from your house is already full of water and there's simply no room in that pipe for another 5 gallons.

So, do the 5 gallon pail test, and in my humble opinion, it's a real good idea to have the main drain line from your house cleared with a snake every 10 years as preventive maintenance.

If you can't remember the last time that main drain line was cleared with a snake, it's time to have it done.

09-09-2012, 07:21 AM
There are many reasons why a toilet would drain slowly, and each has its own cure. But, it is not a vent issue unless you also have a major drain line problem.

11-24-2012, 09:47 AM
My toto was flushing slowly. Tried plunging and snaking to no avail. On reading this forum I decided to buckle down and pull the toilet. To get the water out of the system, I grabbed my shop vac and dried out the tank, then started to vacuum the bowl, and lo and behold the little toy comes flying out!

I love my shopvac. Was I just lucky?

11-24-2012, 12:11 PM
Was I just lucky?

I'm sure every plumber has heard 'nothing was dropped in the toilet' a lot of times when called to fix a slow toilet. You were lucky it wasn't wedged in tighter, but wet vacs are a nice, versatile tool, so, yes, you were at least a little lucky! Toilets just aren't designed to flush rigid things or super big things. Some can handle some amazingly large dumps, but they tend to be softer and more maleable than hard plastic.

11-24-2012, 03:51 PM
Irig: Terry has a great picture in one of the threads of an action figure proudly emerging from the horn of a toilet that he had been called to fix. I guess more toys than most people realize get a trip through the toilet!

10-04-2013, 08:03 AM
I have a ground floor two-bath 20 year old condo unit over a crawl space. The toilets are about 10' apart. The hall toilet works well, but the master bedroom toilet always requires a 2nd flush to get solid matter to go down. The first flush is lethargic, with everything moving slowly around in a lazy circle which produces little effect. A minute later, the 2nd flush is considerably more vigorous and everything goes down.

I have talked to two different plumbers who were in on different occasions to fix other items. They looked the toilet over, but they had little to offer. I think one did try probing the entry holes with a wire or something (didn't seem to have an actual tool available for this). They didn't seem to think a new toilet would necessarily solve the problem. I believe obstruction in the pipe to the street was raised as a possible suspect, but not with much conviction. I don't see how that could be the cause if the hall toilet works OK, as does the problem toilet on that 2nd flush. All opinions welcomed. Thanks.

10-04-2013, 08:47 AM
Open up the back of the toilet and make sure the refill tube is spraying water into the overflow pipe. This fills the bowl after a flush.