I bought some hand-spray bidet kits to add to some toilets. I've done this before on standard toilets, and the installation went smoothly - just remove the input pipe from the port on the underside of the toilet tank, insert the provided T-valve, and connect the hand-spray pipe to the T-valve.

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But in my new house, I have some toilets that are non-standard (Porcelanosa NK One) and which do not give access to the input port on the back of the tank. The toilets are fixed to the ground and flush with the wall, and so there is no good access to where the input pipe connects. I can squeeze my hand back there and kind of feel it, but certainly could not unscrew anything and install new plumbing there.

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As a result, I am stuck with trying to Tee off the other end of the input pipe - the part that comes out of the wall. The pipe size is different than that on the bottom of the toilet port - the wall valve seems to be a 3/8" compression valve, compared to the 7/8" valve at the input port of the toilet tank. So I cannot use the T-valve that came with the bidet kit.

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My question is this - can I just buy an off-the-shelf 3/8" T-valve, insert it between the existing shut-off valve and the input pipe that runs up to the toilet, and connect the hand-sprayer to that T-valve?

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Is there any reason such a T-valve will be unhappy having a hand-spray attachment on it? Will the pressure be significantly different at the end of the hand-spray attachment? It won't have the on-off valve that the provided T-valve does, but I never use that anyways (and if I did need to turn off pressure to the hand-spray - say, to remove the end and de-scale it - I could just turn off pressure to the entire toilet).

2 Answers 2


Keep in mind that you will need to do something about the output side of the bidet valve, and that's not as simple as it seems. You can use a 3/8" tee connected to a standard toilet supply line that then connects to the bidet valve, but the, you will also need a plug for the female side of the valve.

Another option would be to not use a 3/8" compression tee and just run a standard toilet supply line to the bidet valve, then connect a second toilet supply line to the female side of the bidet and have that go up to the toilet.

The problem for both of these cases is finding the proper fitting for the female side of the bidet valve. This is a pipe size that is really only used for toilet valves so fittings in that size are not common.

If you go the first route, you will need to find a 7/8" pipe male plug. I've honestly never seen one of those. If you choose the second option, you can use a "toilet supply line extension hose". Those are rare, but I found at least one example online (it is only 6" long, however).

Also, if you're idea was to not use the bidet valve and connect the sprayer directly to the 3/8" compression tee, that won't work either. Sprayers use another rare thread pattern that you won't find fittings for.

  • Ah - that sounds like a great idea (the extension). Let me try that and see how it goes...
    – Doug
    Commented Aug 29, 2019 at 22:33

You should be able to do what you propose because the adapter/valve that came with the unit does not appear to have any sort of pressure regulator built into it, meaning it appears to be designed for normal household pressure (btw this is not the case with all hand-held sprayer units).

Because the consequences of failure could be catastrophic (e.g. flooded house) I would hook it up but closely monitor it for a while to confirm no leakage, hose swelling, etc.

Oh, and turn it off when you go on vacation...

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