Fitting 40mm non-return valve in ensuite bathroom

[curium]

Hi

I'm fitting a new shower tray and basin into our ensuite.

Previously, in the old suite, we occasionally got bad smells from the shower waste. I assume that this was due to it being joined to the waste pipe coming from the basin before the common pipe joins the stack.

I've purchased a McAlpine 40mm NRV which I'm told will help prevent this by allowing air into the system and so prevent the traps from being syphoned.

I want to know at what point should I attach the NRV. It's joined by a compression fitting and the bathroom is completely empty at the moment so, within reason, I can fit it anywhere.

Due to the symptoms experienced previously I am thinking of putting it on the run of pipe coming from the shower waste before it joins the waste from the basin to fully protect the shower trap from syphoning but I've read that the NRV (and compression fittings generally) should be accessible and once the shower tray is in it will be difficult (not impossible) to access.

Another option is to place it on the run of pipe coming from the basin before the shower waste joins. Will this be as effective at preventing syphoning? It would be easily accessible in this location?

Thanks

 

[Steelmasons]

If you're replacing the bathroom suit then correct the issues with the wastes at the same time , if you don't know what you are doing then seek professional help as in a plumber.

 

[just pumps]

I`m thinking the Osma waste valve would be better than the Mcalpine as it self closes.
Screwfix 3962k.

 

[Hugh Jaleak]

An NRV as in non return valve will not allow air in. Are you getting confused with an AAV, Air Admittance Valve?

 

[curium]

If you're replacing the bathroom suit then correct the issues with the wastes at the same time , if you don't know what you are doing then seek professional help as in a plumber.

If only it were so simple!

This shower room has seen two plumbers. The first was the original building firm. The property is a 'new build' around 20-25 years old. It was refitted around 7 years ago by a 'bathroom fitter'.

Both saw fit to share a 40mm waste between the shower and the basin. This arrangement does not appear to be unusual.

The 40mm waste then runs into a stack via boxing. I can see why it's been done this way as the room is so small that running two separate 40mm pipes is not really an option.

I don't hold much hope for a third so I'm attempting this job myself and thought a DIY forum would be a good place to get advice.

An NRV as in non return valve will not allow air in. Are you getting confused with an AAV, Air Admittance Valve?

Thanks for that. Perhaps I've been misled by the description including the prevention of sewer smells entering the property.

What I really want is a way to prevent water from the sink siphoning the trap on the shower.

Would an air admittance valve need to be raised above the sink? This would be unsightly. Are there any other solutions?

Thanks.

 

[oilboffin]

Try fitting a hep2o valve much better.Bob

 

[endecotp]

I think you may find other threads comparing the waterless traps (hepvo) vs. anti-siphon traps.

 

[Hugh Jaleak]

If the shower waste contains the correct depth of seal then it shouldn't allow smells to exit into the room. Does the shower get regular use?

Basin waste is 32mm and even if that was running full bore, it shouldn't syphon the shower trap, unless there is a partial blockage somewhere once the 2 wastes have combined. With a decent shower trap, and might be wise fit an anti syphon trap to the basin, you shouldn't have a problem.

Just a thought, the stack serving this bathroom, does it vent through the roof or is it capped with an AAV?

 

[curium]

If the shower waste contains the correct depth of seal then it shouldn't allow smells to exit into the room. Does the shower get regular use?

Basin waste is 32mm and even if that was running full bore, it shouldn't syphon the shower trap, unless there is a partial blockage somewhere once the 2 wastes have combined. With a decent shower trap, and might be wise fit an anti syphon trap to the basin, you shouldn't have a problem.

Just a thought, the stack serving this bathroom, does it vent through the roof or is it capped with an AAV?

Nothing visible through the roof outside so I'm assuming that it is capped with an AAV. The stack runs vertically in the corner of the room and is concealed by boxing.

I'm thinking of including a McAlpine Ventapipe 25 on the shower run

 

[curium]

If the shower waste contains the correct depth of seal then it shouldn't allow smells to exit into the room. Does the shower get regular use?

The shower was getting regular use and the smells from the waste were occasional. The new trap is a McAlpine STW7-RB.

 

[Madrab]

Make sure it's accessible, any NRV's/One way valves/HEPvO waterless traps etc need maintained, so you need to be able to get to them.

 

[Hugh Jaleak]

Nothing visible through the roof outside so I'm assuming that it is capped with an AAV. The stack runs vertically in the corner of the room and is concealed by boxing.

When you flush the WC, does the water level ever rise and slowly drop again during/after the flush?

 

[curium]

When you flush the WC, does the water level ever rise and slowly drop again during/after the flush?

Difficult to say. The bathroom has been gutted since October 2016 - so I really can't remember. I'd have to say no since I can't remember it specifically.

Missus is threatening all sorts if I don't get it finished so I'm now in a hurry but want to incorporate something to potentially deal with this.

I've ordered a McAlpine Ventapipe 25 which I'll stick on the shower waste run to protect it from siphoning.