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I'm plumbing my new kitchen sink and due to switching to an undermount sink, there isn't quite room to fit in a standard P-trap - it ends up too low relative to the waste pipe by about 3 cm. I can't really lower the waste pipe as it exits an external wall quite high and we're in a flat. However, I think I could fit in a running trap instead (image attached) as it doesn't drop any real distance.

Given this is also a 40mm diameter tap with a 75mm water seal (standard for UK sinks), would it serve as well as a traditional P-trap? I can't find much info on them online which makes me think there may be some major issue I haven't envisaged.

Running trap

isherwood
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Tom H
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4 Answers4

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The disadvantage is that they're not as self-scouring as a direct p-trap. Particulates that settle into the trap are unlikely to be washed out. Over time these have a greater chance of accumulating and clogging.

To mitigate that, code in some places will require that any running trap must have sufficient cleanouts and be accessible.

If it's under the sink and you can easily unscrew and drop the trap for cleaning, then not a problem.

BowlOfRed
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Considering that many double-bowl sinks and virtually all bathtubs have essentially this, I can't imagine you'd have a problem. I assume proper slope at all points.

isherwood
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In normal operation it behaves the same as a P trap . This style is easier to open in a confined space if you need to clean it out. They're quite common in UK kitchen plumbing. My kitchen (from memory) uses these parts but the pipe then turns vertically down almost immediately. My utility room has very much the setup you're talking about.

Chris H
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I wouldnt risk cleaning tools with plaster tile grout or any such thing in a tub or shower where access to the plumbing is difficult some grout/ thin sets etc actually hardens even under water DONT EVER LET WORK MEN WASH TOOLS IN THE TUB IF NOT AFTER THEY LEAVE YOU MAY FIND THE DRAIN CLOGGED ....I worked at a house once where a new tub was installed and the tiler must have dumped the dirty water in the tub unknown to me because later the drain was clogged and I saw HELL OH HELL to clear it; everything was new so theres no other reason why that drain should have clogged even before the job was done

Frank O'Donnell
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