- The FAQs on Sewers
- What can go down the drains?
- Why can't everything go down the drains?
- How can I know what should and should not go into the sewers?
- A little bit can't make any difference, can it?
- Why should I change when everyone else is still doing it?
- Sanitary things have to go down the toilet, don't they?
- It's always been done that way. What's changed?
- Am I supposed to pour paint down the drain or not?
- Can I put any garden rubbish down the gully trap?
- Can some garden chemicals go down the gully trap?
- What about waste concrete? It won't harden down there.
- It's 99.9% water in the sewers. How can 0.1% cause a problem?
- How big a problem is a sewage flood anyway?
- How big a problem are tree roots?
- Won't this Fat Trap in the kitchen smell?
- Won't hot water get rid of it?
- The product says it is flushable, but you say nothing should be.
The FAQs on Sewers
Dear Visitor,
As with most websites, these are not really "frequently asked questions". They are mostly what we think you are likely to want to know.
If you do have a question, send your question to us and we'll answer it. If the question is asked frequently, then we'll put it here.
| What can go down the drains? | The sewer is only designed for a short list of items. Basically, it is for human "natural" waste and toilet paper, the water you wash
yourself and your clothes in, water from cooking, and water from washing up pots and plates but without all the fat,
oil and food scraps.
Cooking oil is one exception. Oil sticks to the pipes, things stick to the oil, and blockages build up. It isn't as bad as fat but it's similar. It doesn't flow well in the cool pipes so ends up coating them. That coating gets pushed along by flowing water and solids rather than floats away on the top of the water. Cooking oil and fat should be stored in a Fat TrapTM and then put into the household rubbish for landfill. Big exceptions are hypodermic needles, medicines and some chemicals. 
Where you don't have an arrangement with your pharmacist for your "syringes and needles" you can go to the: Needle Exchange Programme. Other people should contact their local pharmacy for advice. Medicines go to any chemist, and chemicals to a council transfer station. |
| Why can't everything go down the drains? | If it was built so everything could go down then you couldn't possible recycle any of it and the mixture could be dangerous.
Substances need to be handled correctly to be recycled, and that means they need to be kept separate from other substances. There would be chemical mixes that are poisonous to the sea and impossible to spot and neutralise. Some of the mixes might be explosive. Also some of the objects that go down are dangerous to the sewerage workers. Hypodermic needles are a good example. Razor blades are another. They can break out of the plastic holder during processing at the treatment plant. |
| How can I know what should and should not go into the sewers? | Basically, if it is reasonable to put it into a rubbish bag then it is not right to put it in the sewer.
Chemicals are a big exception. If in doubt, contact your Local Authority Helpdesk for advice.
The toilet is the most likely place for a wrong item to come from. Usually, it is an object so keep a bin in the bathroom and put it in that. Keep another bin in the toilet if that is in a separate room. You might need to wrap it in a wad of toilet paper or facial tissue first. Empty bins at least once a week. Medicines should go back to the chemist. A lot of medicines kill bugs and there are really useful bugs at the treatment plant that decompose human waste. You don't want to kill them. They're doing a good job for you. In the kitchen, pour fat, oil and grease into a Fat Trap and when that is full follow the instructions on the label for putting the contents into a container for the rubbish bag. Use kitchen paper to wipe food scraps and greasy stuff off all pots and plates before washing them. Put the kitchen paper in the rubbish bag. Consider putting vegetable scraps into a composter or a worm farm. You can't put animal products such as grease, fat, meat scraps, etc into a composter as they are no good for the garden and they attract vermin. You can't bury animal products either, as rats are excellent diggers. Garden chemicals and rubbish shouldn't go down the gully trap. The chemicals do the same as medicines - they kill the bacteria that sort out all the yucky stuff at the treatment plant. You don't want to go killing them. Your garden rubbish just bungs up the drains and sewers. It isn't just garden chemicals that shouldn't go down the gully trap, though. You can wash paint brushes over your gully trap but you can't pour paint down safely. Remember, your drain is your responsibility when it blocks. You pay for it. Don't put any solid things down there. If in doubt, contact your Local Authority Helpdesk for advice. |
| A little bit can't make any difference, can it? | Only if you are the only one doing it.
It isn't just you polluting the sewers, you know! There are thousands of people like you, and you're all doing the same thing. Remember: A load of "little-bits" equals one large "lot-a-bit". Someone's going to dump the "little bit" that is the "last straw" and blocks a pipe. Assume it'll be you. Don't do it. |
| Why should I change when everyone else is still doing it? | Of course it makes only a little difference when you change your habits and they don't. Everyone else must change too.
Think! If everyone says that they are going to wait until everyone else stops then we have a Catch 22 situation. Life will
never improve. Make the change.
The thing is, if you change to doing things properly then you can feel wonderfully smug and say "Oh, I don't do that any more!" when there is a problem caused by "the others". It's worth the effort of changing just for that alone. |
| Sanitary things have to go down the toilet, don't they? | No they don't! Who told you that?
It all ends up at the treatment plant. "Treatment" means that the non-human-waste is filtered out and trucked to the landfill. The rest is stored in ponds containing bacteria that convert it to something less offensive. The results of that are also then trucked to the landfill. The stuff that is filtered out includes all of your sanitary things. They are "uckky" when they go in and "evil" when they come out! The bugs there are for "eating" human waste, not human diseases, blood or anything else. Put all your sanitary things in a plastic bag and put that in the landfill. The experts want it to go directly to landfill via household refuse sacks, not via the sewer. |
| It's always been done that way. What's changed? | It was always wrong but it was tolerated. Now it's getting intolerable. Time for everyone to change.
The world is improving. Bit by bit, how we live gets better but more complicated, and we all have to adapt to that. It's time to do things properly. The Local Authority has got around to sorting out how the sewers are used. |
| Am I supposed to pour paint down the drain or not? | Paint, no. If there's only a little then leave the lid off the tin and let it dry out. When dry, put the tin in the
household refuse. If there's a lot, ask around if anyone wants it. Try local schools and other organisations. Some paint
stores, like Resene
and Enviropaints, will take some paint and recycle it.
Cleaning the brushes and rollers is a different game. If possible, use water-based (acrylic) paints, and wash out with water. In all cases you can clean your brushes and rollers and let the cleaning water go down the sink or gully trap. If the paint is acrylic and there is some waste ground (yours!) that you can pour the cleaning water onto, then do that. Oil-based paints require solvents to get the paint out of the brushes or rollers. Did You Know? The paint doesn't dissolve in the solvent. It is floating around in it. You can leave it to settle, pour off the solvent, and use it again! You just have to get rid of the paint-sludge in the bottom. If you use solvents for your brushes it is okay for them to go into the sewer. The alternatives are worse. Solvents pollute the streams and sea if you put them in the stormwater drains. Solvents are very inflammable. If you put them into the household refuse they will create a fire or explosion hazard when they leak, either in the truck or in the landfill. It's best to dilute them in the sewers. BTW. They can't recycle the steel so don't put the tin out for recycling. The refuse people wouldn't appreciate paint leaking everywhere, anyway. |
| Can I put any garden rubbish down the gully trap? | No. The drain pipes are only 100mm in diameter, the same size as a margarine tub. Those in the street are 150mm, not
much wider. They are too easy to block.
There are narrow points in the sewers where fat, oil and grease collect. Wads of grass or leaves can block it up and then the sewage flows out. There could be one just down the road from you. The sewage will come out of the very gully trap that you put the leaves down. Serves you right? |
| Can some garden chemicals go down the gully trap? | No. They can kill the bugs at the treatment plant that treat the sewage. Then they have to start again.
Far worse, there is no way on earth that they can test the water, find out what you put in there and magically get rid of it. It goes out of the outfall into the sea. Every chemical you put down there ends up in the sea. Was that a pesticide you wanted to get rid of? Contact your Local Authority for advice. They are likely to tell you to leave them at a transfer station or landfill site. There'll be a proper way to get rid of them. |
| What about waste concrete? It won't harden down there. | Yes it will! Concrete has to be kept wet to create a higher quality result, though excessive water results in a reduced
quality. The Romans knew how to make concrete that can set properly underwater.
Once it starts to cure it will continue. It won't be the best concrete down there but it's in your drain for good. That's a narrow point you've made, waiting for other rubbish to fill it and whoops a new garden feature, a sewage fountain. You've created your own "natural wonder". |
| It's 99.9% water in the sewers. How can 0.1% cause a problem? | Well, yes, of course it can. Part of that 0.1% is sticky fat, oil and grease. You know it can build up and block
pipes because that's how blocked sinks happen.
The other part of that 0.1% bits of rubbish sticks to the first part and makes for a really good blockage. And thin, flexible things like backing strips off panty-liners and condoms get through the filters to the sea That 0.1% causes problems. |
| How big a problem is a sewage flood anyway? | Firstly, raw sewage is full of diseases. There are always some people who are sick and at home. The diseases and the
medication are excreted in human waste and go into the sewer. Every kind of sickness currently on the go ends up in the sewage.
When there is a blockage, this all comes out at the lowest point above the blockage. This can be a manhole that "pops". The sewage then flows to the nearest stormwater drain, which will empty into a nearby stream or river. Stormwater is not filtered or treated so raw sewage pollutes the waterways all the way to the sea. If not a manhole, then it comes out of someone's gully trap and floods their pathways and garden. Some of this will go straight into the house's stormwater drains. The rest has to be shovelled up by the Local Authority and taken to the treatment plant for processing. Cleaning up will involve hosing it down where possible and that will go into the stormwater drains. What remains in the soil will have to decay naturally. If not the above, it comes out of a toilet and floods that part of the house. The rooms affected are wrecked and will require the walls ripping out and replacing where the sewage has got under the skirting boards and behind the gib. The flooring will need replacing. How big a problem is it? You can work it out roughly, eh? |
| How big a problem are tree roots? | Tree root problems can occur around septic fields and sewer lines.
Trees such as willow, maple, and elms should not be planted near a septic field.
Tree roots are often incorrectly blamed for plugging and breaking pipes.
Roots can not exert enough pressure to crack a pipe. Natural settling, age, and wear cause pipes to crack.
Leaking pipes encourage roots to grow into the area and to penetrate through the cracks.
As roots increase in size, cracks widen and breaks occur. Source: www.ces.ncsu.edu - Problems with Tree Roots Extract from www.treeworld.info pdf "Tree Roots, A Growing Problem" (259kb). " Trees Versus Pipes Trees provide pleasant shade around the home and are friendly to our environment, but tree roots can create havoc with the underground sewer system. Tree roots are currently [2009] responsible for the majority of Melbourne[, Australia]'s sewer and drain blockages. These problems are most common in household properties. For example, roots of poplar trees have been found in pipes more than 30 metres beyond the tree base and like other 'problem species' such as willows, figs, rubber trees and large eucalypts, they can also damage buildings, footpaths, fences and pipes. With new design standards allowing sewers to be constructed at a shallower depth, the risk of tree root infiltration is increasing. However, it is a problem which can be avoided if care is taken when selecting trees and deciding where to plant them. A Costly Problem Few people realise just how aggressive tree roots can be in their endless search for moisture and nutrients. Your property sewer pipes are a prime target, and if there's the slightest way in through the smallest fracture, the tree roots will find it. " Note: The PDF linked to above will provide an extensive list of trees and bushes that may be safely planted by drains and sewer lines. It will also provide two extensive lists of trees and bushes which should not be planted closer than 2 and 3.5 metres from a pipe. |
| Won't this Fat Trap in the kitchen smell? | No it doesn't smell. Bacteria create smells, and they need to work for a while to get to that point.
The used kitchen oil and grease that you collect has just spent several minutes at a high temperature. There are no live bacteria in it, though some could have fallen onto it from out of the air after it cooled down. If the oil or grease is poured into the Fat Trap before it has cooled down then there will be no bacteria in the Fat Trap. Occasionally, bacteria from the air does get into the Fat Trap - from coled oil or grease, or from the air during the minute or so it is open. A mould then forms on the surface. In this case you can either pour some more hot oil or grease on it and entomb it - without air it can't survive - or quit now and put all of it in a scrap container and put that in the bin sooner than planned. |
| Won't hot water get rid of it? | Kitchen Grease doesn't dissolve in water. It always stays separate from the water, and when blobs of grease touch they merge into a bigger blob.
Hot water makes solid grease become liquid and makes liquid grease flow better. Hot grease cools and sets on the pipes between 6 and 7.5 metres from the plughole. That's where plumbers go looking for it. Dishwashing detergent gets between surfaces and grease and so dislodges it. As soon as the detergent washes off the grease, the grease sticks to the pipe. |
| The product says it is flushable, but you say nothing should be. | There are a few products that the manufacturers believe or hope will dissolve in the sewers.
We wonder how they tested that.
Everything put into the sewer has to be extracted at the Treatment Plant. Then it is trucked to the landfill. It will cost less money on the rates if you send it there directly. We believe that sending rubbish to landfill via the sewers is a dumb idea. Treat flushable items as non-flushable. Don't treat the toilet as a "wet bin". |