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Tim JA
Tim JA, Engineer
Category: Plumbing
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Experience:  Owner at Self-employed
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I want to install a Grohe manual bidet. Inlet is 3/8. I need

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Hi. I want to install a Grohe manual bidet. Inlet is 3/8. I need to split water inlet to toilet. Not sure what valves to use.
JA: Do you know the model of your Grohe? Have you talked to a plumber yet?
Customer: I haven’t talked to a plumber yet. There’s only one model. Number is ***** Ceramic. 39648SH0
JA: How long has this been going on with your Grohe bidet? What have you tried so far?
Customer: just purchased it. Want to purchase right connectors.
JA: Anything else we should know to help you best?
Customer: no
Customer: replied 1 year ago.
Hi. This is the current set up.
Customer: replied 1 year ago.
Another photo from the other side.

Good afternoon, welcome to the Technical section in JustAnswer; my name is ***** ***** I will help you today.

This is fairly straightforward, and I can give you a list of parts to use/buy. I presume that this is the bidet seat, not a bidet. The manual shows a flexible hose connecting to a 3/8" male spigot on the pan - did that flexible hose come with the kit? If so, is it 3/8" or 1/2" female on the other end of the hose?

If you receive a phone call offer, please ignore it - these are system generated and outside my control. My understanding is that you won't be charged if there's no phone call.

Customer: replied 1 year ago.
No flexible hose supplied.

Follow-up question: is there any movement on the white Hep2o elbow that's current tight up against the wall? Will it pull away from the wall at all? Perhaps about 30mm?

Customer: replied 1 year ago.
No fixed to wall. And yes bidet seat.

OK. I'll put together a parts list. I'm working on a few questions in parallel, but I will get back to you this afternoon.

Customer: replied 1 year ago.
Thanks Tim.

Parts list:

- flexible hose
- Hep2o shutoff valve
- Hep2o 15mm equal tee
- Hep2o demounting tool


In addition, some things you might already have, but if not you'll need to get:

- 0.25 metres of 15mm copper tube
- PTFE tape

After you've installed the bidet seat, follow these steps:

1. Cut three 80mm lengths of copper tube.
2. Make on** one end of one tube to the 15mm end of the new flexible hose.
3. Push the other end of that copper tube into one end of the Hep2o shut off valve.
4. Push one end of the second tube into the other end of the Hep2o shut off valve.
5. Push the other end of that second tube into the centre of the equal tee.
6. Push one end of the third tube into one end of the equal tee.
7. Shut off the water supply at the main cold stop cock (or a valve on a gravity supply, if that's what you have).
8. Flush the WC to take as much water out of the pipe as possible.
9. Using the demounting tool, remove the length of copper tube that leads to the WC isolating valve.
10. Push that copper tube into the remaining open end of the equal tee.
11. Push the remaining end of the third copper tube into the old elbow.
12. Couple the 3/8" end of the new flexible hose onto the bidet seat spigot.
13. Close the new shutoff valve.
14. Reinstate the water supply and check all connections.
15. Open the new shutoff valve and test the bidet seat.
16. Check all connections again.

** If you haven't made on compression fittings before, let me know and I'll send you the steps.

Customer: replied 1 year ago.
Thanks Tim. I haven’t made in compression fittings before. Could you send me the steps?

OK. You need good quality, accurately fitting open-ended spanners or adjustable wrenches. I'll see if I can find a YouTube video that illustrates the principle, but the steps are:

1. Remove the nut and olive and slide them onto the tube.
2. Fully insert the tube into the fitting and do up the nut until hand tight.
3. Brace the fitting with one wrench and use the other to turn the nut until it's hard to turn, then go about 1/8 turn more.
4. Brace the fitting the other way, and undo the nut - it should release after less than 1/4 turn, then undo with fingers.
5. Check that the olive cannot move on the pipe; if does then repeat steps 2 to 5.
6. Wind about 5 turns of PTFE tape on the wet side of the olive.
7. Reinsert the pipe and hand-tighten the nut, the tighten with spanners.

Do not put PTFE tape on any threads, or on the dry side of the olive.

If you follow these steps then a fitting can never be pushed off a pipe by water pressure, because the olive is crimped onto the tube by this method.

The question of "how tight" is a matter of feel. It's hard to convey if you've never done it. If the joint leaks, you haven't done it quite tight enough.

I'll look for a video now.

Customer: replied 1 year ago.
Thanks. I have the right wrenches. The space is tight behind the loo but should be able to squeeze in with wrench and fittings.

No! If you follow my steps you don't have to do any squeezing in anywhere!

Make on all compression connection out in the open, where it's easy. Plumbing all about making the job easy, to reduce the chance of making a mistake.

Customer: replied 1 year ago.
Oh ok. I’ve a lot to learn but looking forward to trying it out tomorrow after getting the parts from Screwfix in the morning.

Here’s the first video. Do what this guy does but stop at 1:10. Do not apply the tape like he does after that.

Customer: replied 1 year ago.
Thanks. He does use a lot of tape. But your advice is 5 turns on the wet side of olive over the bit of copper pipe that goes into fitting?

Yes. The tape should be centred on the line where the olive meets the pipe, which results in half of the tape being nicely between the olive and the chamfer of the fitting that it seals against. The other half of the tape is around the pipe just inside the fitting.

I'm going to have to make a video - I've just looked at about 10 videos on YouTube and they're ALL hopeless. The least bad is the guy in the video above - at least he does the first part correctly, in crimping the olive onto the pipe and then removing it to apply the tape.

Just make sure you don't overcrimp. It's better to have to repeat steps 2-5 until the olive doesn't move, than overtighten on the first go.

Customer: replied 1 year ago.
Thanks Tim. Very helpful. Now explains why I had small leak when fitting a Grohe kitchen tap with 3/8 flex hose for my parents last year. Used wrong fittings and used tape on threads. Should have just used right compression fitting rather than brass reducing hexagon bush and something else to make a Heath Robinson affair. Hence wanted to make sure had right layout for this. Thanks again. If any problem during fitting how do I contact you?

Learning is living :-)

Bushes are a nightmare. Sometimes they just have to be used, but they're nearly always troublesome.

You can keep posting on here. The topic will stay open for days, and if it did get closed then you can open a new one and mark it for my attention. If you're happy with my assistance, please rate me using the 5 stars at the top of the page. The customer's rating is what enables an expert to be paid for their time, so I hope I was helpful to you.

Tim JA and other Plumbing Specialists are ready to help you
Customer: replied 1 year ago.
Will do. Very helpful. ��

Thank you for your rating :-)

... and your kind bonus :-)