S Trap toilet - vent capped, not flushing properly

sumstyle, Jun 18, 4:30pm
Hi all, I had a plumber replace a s-trap toilet, and cistern in December. The previous one was vented out through the wall, so I bought another vented pan. However, he capped the vent, and the builders took out the pipe through the wall. The toilet doesn't flush fully on a regular basis.

Could this be because on the lack of vent, or will it solely be because of the replacement cistern? He also replaced our 2nd toilet (p-trap) with same type of cistern and we have no problems with that one flushing successfully.

Any clarification would be helpful.
mm12345, Jun 18, 6:18pm
What do you mean by "doesn't flush fully"? Not enough water flows from the cistern - or the cistern doesn't drain/empty properly?
Did he "cap" the vent - or put a valve in? Normally, I'd expect that if the external vent was removed, then an air-admittance valve might have been fitted - so the vent in the pan wouldn't be "capped". But it probably depends on what other vents are there in the sewer - the valve might not be needed. A quick and easy solution might be to replace the cap with a valve, but that may not be appropriate or even legal - other nasty things might happen. You need to call the plumber - if the pan isn't draining and that's because of a venting issue, it needs to be fixed.
pauldw, Jun 18, 6:25pm
What do you mean by doesn't flush fully? If you tip a bucket of water into the bowl what happens? The current thinking is that separate venting isn't required if the sewer pipe that the toilet empties into has a vent close by.
sumstyle, Jun 18, 6:50pm
When I flush it doesn't remove the paper or solids from the pan. the cistern empties itself in the flushing process, but the pan is not cleared of all the contents.
pauldw, Jun 18, 8:20pm
How many litres is the pan designed for on full flush? Your S trap pan could be a 6l while the P trap and both cisterns are 4.5l. The cistern may have an adjustment for flush volume.
nzjay, Jun 18, 8:23pm
Does the water level in the pan rise significantly when flushed and then slowly go down to normal? If this happens it could be a venting problem.
If the water has poor flow from cistern to toilet bowl when flushed it is a different matter and could be some obstruction in the flushing pipe, the wrong sized pipe, cistern water level too low, poor design of pan (a cheapie) etc.
Either way, I think you need to involve your plumber again.
sumstyle, Jun 18, 9:10pm
Excellent, thanks everyone. I didn't know if the vent was just for noxious gases, or if it might affect the flushing/purging action.

pauldw - that's also really interesting too, I never knew that about the different litre capacity.
pisces47, Jun 19, 2:09pm
The only vent I have seen is the vent from the old type cistern and this is for overflow if your cistern water stop seal leaks. The new cisterns have the overflow going into the toilet through the flushing mechanism. This will have no effect on how well the toilet flushes. Take off the top of the cistern and see how full the tank is, if it is low you may need to adjust to the fill line to get a full flush
sumstyle, Dec 11, 8:46pm
No, this is a vent off the pan, not a vent from the cistern pisces