Plumbing in the Home/Flushing Low Flow Toilets


I have a low flow toilet about two years old and it will only do a first time complete flush about 20% of the time. Does not matter if solids are present or not. Short of buying a new toilet is there something on the market that I could add to help with the flushing, or any other suggestions you can pass along. Thanks.

Hello David,
There are number of things that could cause problems when flushing the toilet. The actual mechanics of a toilet flush are pretty much set in the design when it is cast. There is a trap cast into the base of the toilet and when you flush, the water causes the trap to siphon everything out of the bowl. If anything interferes with the siphon, the toilet will not flush properly. Make sure the toilet mechanicals are properly adjusted so that the maximum amount of water allowed is being used.

Depending on how it was installed, it is possible for part of the wax ring to get displaced and partially block the toilet outlet or the waste line inlet.

All fixtures that drain into the waste system require proper venting. If the venting is not been done correctly within the waste and vent plumbing system, the fixture won't drain correctly. It's sort of like holding your finger over the end of a straw, the water will not drain out of the straw until you break the vacuum by lifting your finger. A vent line does much the same for a plumbing system.  It is also possible that a vent line is plugged by insects or vermin entering from the top.

There could be a partial blockage in the drain line itself. Snaking the line might help.

Good Luck,

Plumbing in the Home

All Answers

Answers by Expert:

Ask Experts


Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


Retired, Licensed General Contractor with Plumbing license. Active Home Inspector, Litigation Consultant and Infrared Thermographer, Online Marketing specialist.

Publications "Rain Maker" as "Inspector Dana", about making money online.

30+ years in the building trades, Licensed General Contractor (Retired), Certified Infrared Thermographer Internet Entrepreneur, Amazon & eBay Merchant (deals-by-dana)

Awards and Honors
Listed FHA Fee Inspector, FHA 203(k)Consultant, HUD Mobile Home Inspector

Past/Present Clients
Home buyers, sellers and owners, Investors, Commercial roofing companies (infrared roof scans for moisture intrusion, Litigation Consulting for "Slumlord" laws in SoCal

©2017 All rights reserved.

[an error occurred while processing this directive]