View Full Version : The Differences of Drain Systems between US and Europe

05-06-2010, 01:17 AM
I googled the case above, written and/or illustrated issues, but could'nt find out any info even clue.
I want to learn why siphonic toilets (both pressurized system or not) installed almost everywhere in US[/B][/B], and why gravity-types (non-siphonic) in all Europe... I wonder what kind of differences in drainages, pipe transmissions&dias, flow rates, water pressures and vacuum factors etc.
Thanks for your interests,

05-06-2010, 02:40 AM
That wasn't always the case.
Toilets in the USA used to mainly be washdown bowls. It was when they started using less water that they added the siphon jet to add performance to the flush.
There are still some models sold in the US that are washdown, but fewer and fewer.

In the US, because we've always had so much water, we're used to using it.
It's common courtesy to leave a clean bowl for the next user.
I believe that in other parts of the world, they don't worry about that.
Here, if there is anything left in the bowl, they will flush again to make sure it's clean.
We tend to take showers every day too.
We use more water per capita than anywhere else in the world.

05-06-2010, 05:41 AM
Unless the toilet is a "dry hopper" type, which has been extinct here since the 20's, ALL toilets operate by siphonic action. The differences is in HOW they iniitiate the siphon action.

05-06-2010, 06:52 AM
I have to say that I want to understand why there is a necessity for siphonic flushing action in US. I know about the benchmark of US and Europe, the designing, shape and diameters of the trapways, drain carry distances according to the flushing and water consumption quantities but it is not adequate answer.
What about your drain system, angle and diameter of waste pipes etc.
Let's consider in another view, is there anyone who lived and worked both in Europe and USA?
Or can you redirect me any other people interested in plumbing fixtures and drain systems?
Thanks a lot!

05-06-2010, 08:11 AM
Stay here, and continue to post what you know, in greater detail.
Within a few weeks you will have attracted attention from the knowledgeable players you seek to engage.
They will respond with posts of similar detail and depth of knowledge.
Yes, there are many people who have lived and worked both in Europe and USA.
I have seen many of them posting in this forum.

I have two Geberit in-wall carriers. One has a Duravit bowl, the other has a Catalano. Each carrier and bowl is identical to what is sold and bought in Turkey, in Europe. Therefore I conclude that HJ's explanation is closer to the reality here than your description which uses the word necessity, saying "... want to understand why there is a necessity for siphonic flushing action in US." By the way, Canada has the same as the USA, in terms of drain. Mexico too, as far as I know...


There may be a simple less complicated answer to your questions: the market makers in North America have sold products which seem to be common now. Market makers made the market what it is.

Hope this helps. I am not an expert in drain-science.

05-06-2010, 08:13 AM
The water goes into a pipe everywhere you go.
After it leaves the bowl, it's all equal.

05-06-2010, 03:11 PM
Most (all?) modern toilets have a trap built into them. To get the thing to flush, it needs the assistance of the siphon. As HJ mentioned, it is how you generate that siphon that differentiates the various flushing mechanisms available. Once the siphon is established, that sucks the water and waste out of the bowl. Once enough of the water is siphoned out, it sucking air causes the siphon to break, and the flush to stop.

05-10-2010, 02:54 AM
Let's change the question; - Siphonic toilets contain much more water in bowl with larger water surface area. Is this derived from just a cultural effects or drainage effects, or something else? What should be the cause?

05-10-2010, 05:50 AM
I'm not a plumber, but I have lived in Europe and the USA. In Europe (at least in France), the toilets tend to be rear-outlet instead of bottom outlet. I'm not sure what the Euro toilets have in terms of a built-in trap, but it must be very shallow. The Euro toilets have a very small water spot (basically just enough water to cover the outlet of the toilet). The Euro toilets also must use a large flush valve as they seem to dump the water pretty quickly into the bowls. In fact, splashing seems to be a problem in my experience.

You see a varity of toilet designs in Europe. Often, hotels will have the tank inside the wall (space is a big issue when converting these old buildings to hotels). Other toilets will have a pushbutton on the top of the tank or something that you pull up. You don't typically see the trip levers that are common in the USA.

For people outside of the USA, most North American toilets have a deep internal trap which keeps a good amount of water in the bowl. Older toilets (like my 42 year old American Standards) used a lot of water (3.5 - 7 gallons (13 to 26 liters) per flush, depending on the age of the unit). These toilets kept a high water level in the bowl. Newer toilets in North America use 6 liters or less per flush. As a result, the designs were changed so that there is not as much water kept in the bowl, but the water spot still tends to be much larger than the European designs that I have come across.

For the toilets, the water level only depends on the design of the toilet itself (the design of the built-in trapway). It does not depend on if the toilet is washdown or uses a siphon jet.

In terms of the plumbing beyond the toilet, I don't really know in terms of what is done in Europe. I did not do any plumbing there and only saw limited exposed pipes. From what I did see, it does look similar to how things are done in the US.

Alan Muller
05-18-2010, 08:03 AM
My impression:

Sometimes when people say "washdown" they mean a toilet that puts all the flush water in from the rim and doesn't have a syphon jet to fill the trap and start the syphoning.

Sometimes they mean a toilet that isn't "syphonic" at all.

Big difference.

Almost all US toilets have been syphonic, meaning that once the trap is full and flowing it will flow until it sucks air. This design can empty any amount of water out of the bowl but tends to have a trap ID of around 2 inches, so it can clog. Problem is, with only 1.6 or 1.28 gal available, and some of htat used to fill the trap, there just isn't enough water to refill the bowl very much.

The typical European washdown bowl has a smaller water spot and just washes the contents down under a barrier in the trap. This design tends to have a larger trap diameter so it seldom clogs, but the bowl doesn't stay very clean. This design probably makes more sense as water use limitations get more severe and people get more used to using the brush.....

Ian Gills
05-18-2010, 01:48 PM
European toilets are much quieter since the siphonic action is less severe.

US toilets literally "suck". Plus, European toilets rarely need to fill the trap after the flush. Hence you rarely find a fill tube. The tank just fills. On balance, most people that come to visit us prefer the way US toilets flush but the practicality of European plumbing.

Space is certainly an issue. It's one reason why the waste stack is often on the outside of houses, not on the inside like in the US. It is also quieter and better maintains the integrity of the roof. We use slate roofs, not cheap asphalt and a bit of flashing like the yanks.


Other types of drain are the most interesting. Sinks and baths will often drain, again on the outside, to a back inlet gully with an air gap between the pipe and the gully. The black pipe in the picture above is an example of a gully used for an upstairs sink and bath, below for downstairs. The inlet gully, in turn, goes into a foul drainage run and onto a foul water manhole. It's one reason I had never heard of a sewage back up until I came to the US. I guess you can tolerate waste in your homes more than we can. Toilets drain directly to the sewer.


This is the proper way to plumb a washer and a sink Terry.


But some American inventions did not manage to escape us:


Thanks uSA and your AAV!

05-18-2010, 03:31 PM
Humm, so if afer the air gap, things were plugged up, you'd have your drains washing down the side of the house? WIth the toilets, in theory anyway, if the main line got clogged, you'd still have the toilet overflow. You might have to work at it, but possible. Having lived in various countries outside of the US (four and visited numerous others), I still like our methods. And when it gets to electrical from the UK, I prefer our smaller plugs. Why pay extra for a bigger plug and a fuse for each thing to be plugged in? And, who wants to search for the right fuse, if you do have a problem? (Yanking your chain)...

If the pipes are installed properly, good slope, no dips or rises no excessive turns, it is rare to get a clog. I've lived here for nearly 30-years, and have never had one nor has my mother, which is now going on 55-years in her house. We hear the horror stories here only from the small group that do have problems, but not the millions of people that don't.

Ian Gills
05-18-2010, 04:40 PM
And when it gets to electrical from the UK, I prefer our smaller plugs. Why pay extra for a bigger plug and a fuse for each thing to be plugged in? And, who wants to search for the right fuse, if you do have a problem? (Yanking your chain)...

Now you've overstepped the mark. American electrical is appauling and a mistake of history. You only have 110 volts here because the first lightbulbs invented were these. By the time the Europeans introduced electricity, technology had advanced to produce finer 240 volt filaments. But it was too late for the Americans. All their infrastructure had been built to 110 so there could be no going back.

So everything runs hot here, the wire is extremely thick, heavy and expensive and it is just a waste of time.

240 volts is far superior as are ring mains which (almost) halve the wire guage needed again.

My range in the US uses the same size cable as a service entrance for a big house in the UK. And with a ring main you can safely run a 30 amp circuit on 240 volts using wire thinner than 14 guage. And you don't need a special four wire circuit just because you've gone and bought an electric dryer instead of a (God forbid) gas one. No one has even heard of a gas dryer in Europe! It would be like asking for a gas-powered radio.

You get a lot of power from 60 amps on 240 volts and a lot less heat too.

America is just one big fire risk with suffocated plumbing.

But the weather is quite nice.

05-18-2010, 05:05 PM
Most other places that use 220v, use CB or fuses that protect the wires in the wall, not in the power cord.

Ian Gills
05-18-2010, 06:09 PM
And we do have breakers but they are typically 30 amps.

It is just so much more precise to have individually fused devices.

In the US, if my alarm clock develops a ground fault its gonna take a full 15 amps to trip the breaker which would most likely set it on fire.

In the UK, it would take only 1 amp to blow the fused plug and all the other appliances on that circuit would not be disrupted.

The fridge does not go out when the smoothie maker dies.

Plus we have fuses before the main panel. In the US, if a fault develops on or before the service entrance cable you have to wait for the transformer to blow. And I hear that they tend to just keep giving, which means house fires and flashing power lines. Unheard of in Europe.

Did I mention that we also bury our power lines which means you don't get people complaining on TV that they have not had power for weeks on end when it's windy or there is a bit of snow?

05-18-2010, 07:31 PM
Did I mention that we also bury our power lines which means you don't get people complaining on TV that they have not had power for weeks on end when it's windy or there is a bit of snow?

The US has lots more thunderstorms than the UK. Being underground does not protect from lightning damage, and finding the problem is a lot harder if it does get hit. Plus, you could plop the area of the UK in the middle of the USA and lose it...lots of long distances. There are lots of places taht bury their wires, it's just not the norm.

06-02-2010, 01:21 PM
... Siphonic toilets contain much more water in bowl with larger water surface area. Is this ... cultural ... or something else? ... I think it's what you might call cultural, meaning it's almost accidental (initially) and it became a part of the ambient expectations.

06-18-2010, 01:02 AM
Exposed drains? Really? Even the ancient Romans had buried and in the wall drains. Are you parodying the arrogant European or are you serious? It may work a little better there without as much freezing weather but the design is unhygienic, subject to damage from being exposed and ugly as sh*t.

As for gas ranges, natural gas heating is significantly cheaper than electric in the US, so that makes perfect sense. Why is that so puzzling to you?

Also, many things (such as stoves and dryers) are run on 240v--the things that actually need 240v. Does your clock radio actually need 240v 30a? Appliances than need 240v get it.

As for buried lines? When you have such a tiny country like the UK, it is far easier to use a more expensive process like burying the lines. Look at a map sometimes and the the vast grid that needs to be covered in the US. Also, certain areas do obviously rely on buried lines--you don't see overhead lines in large cities.

06-18-2010, 06:50 AM
Buried lines are an asthetic preference in many cases, or a practical one where snow and storms can damage overhead supply lines and utility poles. It is also a much more expensive way to do it, especially when it comes to relocating overhead lines underground. There are MANY more power outages caused by lightning striking exposed lines than EVER occur with underground ones.

Don't get into the snobbish opinion that the only good ideas come from England or the Continent. My wife's uncle never believed that good beer, cameras, or cars could come from anywhere buy Germany.

Ian from your comments, I believe you also consider the British method of filling a cistern in the attic with a float valve and letting it flow to the faucets with just ONE faucet, usually the kitchen sink, being taken off the pressurized main? As opposed to our "antique" method of pressurizing everything so that when something breaks it floods the house instead of just draining the water out of the cistern? I think we will prefer our "outdated" methods. I am surprised Europe did not agree with Edison and go with Direct Current wiring. Now THAT would have showed us, wouldn't it?

The water area in a toilet has NOTHING to do with the flushing action, it has to do with how MUCH water is required to initiate the action. Washdown bowls required a lot of water but did have a smaller water area. Siphon jet and later reverse trap bowls could be designed with larger water areas, but needed enough water start the flush action and partially refill the water in the bowl. Your basic premise is flawed as to the relationship between water area, American bowls, and European bowls. In fact, they send us their toilets and we send ours back to them and they ALL work exactly the same.