Dutch term (edited): diepspoeler; diepspoeltoilet; diepspoel-wc

The Onroerend Goed Lexicon has:

diepspoeler = washdown closet
diepspoeltoilet = washdown closet


GWIT has:

diepspoelcloset = wash-down closet
diepspoelpot = wash-down closet pan
diepspoel-wc = wash-down toilet

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also found: "washdown closet (washdown pan): A WC (*water closet) where the contents are removed by a flush of water running down the ..." (A Dictionary of Construction, Surveying and Civil Engineering: http://www.oxfordreference.com/view/10.1093/acref/9780199534... )

I think I'd go with "washdown toilet", your context permitting.

see also: https://www.youtube.com/watch?v=n0XzGVDyMKo (for an action-packed video!)

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Note added at 1 hr (2015-08-14 17:48:42 GMT)
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"Now what's the shelf thing all about?

The most shocking thing for many an expat upon their first trip to a WC in Holland is what is commonly known as the ‘inspection shelf’. Thanks to Dutch toilet design, you are given the opportunity to examine your fecal matter before sending it on its way to the sewer. While it is an appalling idea, it is also a practical one. Many diseases and health issues can be detected by examining stool samples. Just as we determine if we are drinking enough water by looking at the colour of our urine, we can see other diet needs and surpluses by taking a peek at our excrement.

The system of having a flat surface in the toilet bowl comes from the Germans. In France toilets have more of a triangle shape, enabling feces to plop right to the bottom of the bowl and immediately out of sight. American toilets have the same idea, but contain a higher level of water so that the excrement floats to the top. In his lecture on toilets and ideology, philosopher Slavoj Zizek, who specialises in ideology and materialism, points out that each society seems to have their own system and each feels that their system is the best.

The flachspeuler (German for ‘flat-flusher’, i.e., the shelf design) may not be the most pleasant of toilet models, but it does have its advantages. Besides the opportunity to do a health check on your latest sample, these toilets save you from being splashed with toilet water with each deposit, and the design and flushing system save water." (http://www.expatica.com/nl/insider-views/Everything-you-neve... )

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Note added at 1 hr (2015-08-14 17:50:42 GMT)
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"August 2003, Nijmegen —

I didn't want to write about the Dutch toilets last time I was in The Netherlands. Well, I'm back; and I can no longer ignore the issue.

Normally, it's good to accept a different culture at face value, and to seek fault as little as possible. The Dutch toilets are just crazy, though, and I still feel that way.

For those who haven't had the privelege of shitting in The Netherlands, allow me to describe. Instead of a bowl, you have a shelf. That's the simplest description. The shelf has a very shallow bowl-like aspect, and a low curved lip toward the front of the unit, where the flush-tube is.

So, you get to take a good look at your stool.

Then you flush the toilet. You'll find one of a diversity of methods, which is kind of charming. Handle, button, bar, panel, chain, rope, cord...? Tank above, tank behind, tank hidden in the architecture? There's no standard. Some toilets even have a bowl. But never mind those.

When you flush the real Dutch toilet, your stool is supposed to wash down that flush-tube at the front. It doesn't always do that, of course.

There should be a toilet brush. If there isn't, something's missing. The brush is not just for the occasional housecleaning toilet scrub. You have to brush that shelf. You might even have to sort of help push that turd down the flush, sometimes. I mean, you can't leave it there.

So the toilet-brush is soiled, sometimes badly.

I don't like Dutch toilets." (http://www.stevenroyedwards.com/dutchtoilet.html )