Installing en-suite -> Couple of questions

[sotal]

Ok we're putting a Shower, Toilet and sink in.

Easy question first - For the shower we have decided on a Jetstream Venturi Effect Shower. Has anybody tried one of these do they really work???


The water feed to the bathroom is no problem, except that the above shower says it needs a check valve and a non-restrictive isolation valve installed on both the hot and cold supply. The only bit that got me unsure was the "non-restrictive" part. I have a pile of isolation valves (standard metal ones that you stick a screwdriver in and turn) are they non-restrictive? They look to make the hole thinner in the middle. Also does using plastic pipe with push fittings make the pipe restrictive??? (the inserts reduce the diameter) - I guess what I am asking is what exactly do they mean by non-restrictive?


And Finally - Waste. We have installed a 4" waste pipe to take the contents of the toilet to the stack. We also need to take the waste from the sink and the shower out, originally I had decided to use a pan connector with a boss connector (think that's the right word) on the bend, but that is too high for the shower. can I put one of the strap on type boss connectors on the side of the 4" waste pipe further down? - What I am worried about is:

a) will the flushing of the toilet suck the contents of the traps out??

b) is there any possibility of waste from the toilet flowing back up into the shower if there was a blockage??

I have seen air-admittance valves to put onto the 4" pipe, but I can't really fit one anywhere - do they do an air admittance valve to fit on the shower waste pipe to stop that sucking the water out?


Sorry for all the questions!

Matt

 

[felix]

If they make the hole thinner in the middle, that's restrictive. I can't comment on plastic pipe because I never use it.

You can put a strap boss on your soil stack but it'll have to be very close to the floor - or do you intend to run it under the boards? I think there's a minimum vertical spacing between entry points on a stack but I don't have the book handy so don't quote me on that one.

Your soil stack should already have an open end at the top so adding an air admittance valve is a waste of time. It will only suck your traps out if that open end gets blocked. An excessively long run of shower waste pipe could do it. To prevent this, use 1.5in pipe for the first two metres or so then open it out into 2" pipe for the rest of the run.

NB: On long, near-horizontal pipe runs take care with the slopes and use plenty of supports. Any sagging will give you a variety of strange problems.

If that soil pipe gets blocked down below you'll have a mess to clean up no matter how you do things!

 

[sotal]

Thanks for the reply Felix.

I probably didn't explain myself brilliantly! I have attached a crude image of where the pipe goes:

The outside soil stack has an open end at the top, but that is quite far away from the bathroom (at least 3m) So I thought that there may be some need to allow air in earlier??? I intend to run the shower waste under the floor boards and then connect into the side of the 4" waste pipe. I have tried to indicate this on this picture (in red):

I was told by someone that you should only ever go into the top of the 4" pipe is this true? (I can't fit the pipe on-top between the floor boards)


If I can't do this I do have an alternative - It just requires me to make quite a large step up into the shower.





Does nobody have any thoughts on the Venturi effect showers? I have searched the forums and found a couple of comments but nothing major!


Still not 100% on this restrictive business. Anybody got any clues on that? Somebody suggested that the shower wouldn't care about the pipe being thinner as long as it flowed straight through. Some isolation valves or taps make the water hit something inside and then go round it??? and that type wouldn't be suitable - any ideas if that is true??

The shower itself uses push-fit fittings so I can't see their being too much of a problem with the bore of the pipe being reduced?

 

[sotal]

I have just found an article saying that I can connect the shower and sink waste to the soil pipe if I use a "deep seal running trap" between them. Anybody got any comments on that?

 

[kevplumb]

why would you need a trap between them

 

[sotal]

apparantley the shower trap could get sucked dry, the deap seal running trap should be OK???

I don't really know you're the experts!!

 

[kevplumb]

so what you are saying is you want to run the basin and shower waste through the same pipe to the stack

 

[Bahco]

The non restrictive valve being referred to is a full bore isolation valve. Other isolators have a reduced bore in the middle.

Run your (anti syphon) basin waste into the boss fitting on your loo and run your shower waste externally to the soil pipe. Fix to a strap on boss.

 

[ChrisR]

This is a non restrictive tap:

When open, its bore is the same as the pipe it connects to. Just used a 42mm on a water main!

The trouble you're going to get into is "pulling" water out of the trap(s).
E.g. a big ball of stuff going down the soil pipe acts like a piston and empties traps it's connected to unless air can get in somewhere else. Same thing happens on smaller pipes too.

There are several types of trap which help/cure the problem. You can use a vented or a resealing or an anti-syphon trap on the basin but not the shower. You could use a Hepworth invention on the shower which will prevent backflow from the basin:

Nb an elbow is listed by it which you'd want for the shower waste.

NB most people use a 1.5" seal shower trap. They don't meet any building regulations, because they're crap.

Look at the traps in the BES cat I took the pics from and you'll see various types.

You would only put a boss into the TOP of a horizontal soil pipe, or you'd block it pdq. Better to take the 2" pipe outside by the side of the 4" and join it in a bit lower down the wall.

If the basin waste goes into the soil pipe near the wc and IT has a suitable trap, that would "do" for air admittance - you might get some funny noises sometimes. The proper solution is a "stub stack", going above the "flood" level with a 4" AAV on top, usually referred to by a make "Dergo".

Might be simpler all round if you got a book out of the library!

Venturi showers are better than electrically heated ones, but not much.

 

[felix]

1) Going into the side of a soil pipe is a bad idea. Toilet crud can so easily lodge in the small pipe. It stands to reason that going in at the bottom is an absolute no-no! You might get away with 45 degrees off TDC, or even 60 at a pinch, but top is best.

2) Running a 1.5" pipe into 2" pipe won't stop dollops of c**p sucking your traps out in this case. You can solve the problem with a re-vent - a small (1") pipe tapped into the top of your new waste and taken to a point on the soil stack higher than any other point of entry. This provides an air bleed to your waste pipe. I would draw it but I don't think I can post pictures from here.

3) Another option, though it uses more pipe, is to take your new waste all the way out to the vertical soil stack. Use the 1.5 to 2" trick and you won't need a re-vent.

PS: For non-mechanical engineers, TDC = top dead centre.