MortarThePoint

This is what I'd want to avoid. In this case the blockage is in the pipe that is going into the wall and down into the branch orientated on its back. Pretty impressive! Before removing the access cap:

Good thought. It's a pig to route the shower to the stack separately unfortunately hence the whole use of the branch. I think I can include an AAV (Class A1) on the shower's 40 or 50mm pipe to ensure the trap doesn't empty.

Is it OK to install a branch as shown below? I can see that there is probably a violent flow within the branch from the toilet direction and wonder if that could cause solids to get left behind or anything. In my specific instance: 'To Stack' end is probably straight into a 90 bend 'From Toilet' would be a 45 bend and some 110mm pipe with then a pan connector inserted like WC-CON8 'From Shower' would be a short length of 110mm pipe (~200mm) and then 40mm or 50mm pipe. I don't want the 'From Shower' side to get blocked by solids left from the 'From Toilet' bit. I assume the following configuration is less desirable than the first:

Below is a picture of how all of this as ended up. You can't see that below HCF there is the 50mm shower waste joining, but just above the HCF you can see the two 40mm waste pipes (bath&basin from this room and shower&basin from next room). Also out of view is a 32mm pipe that forms a possible future connection point for a loft toilet (via macerator). The grey and black 90 elbows bring the stack to the wall and an AAV goes into the top. On the right of the image, you can see the 90 bend going into the wall for connection to the toilet in the next room. Around the middle of the photo is the connection point for this room's toilet. Rodding access is perhaps not as good as I could have done (90 bend through wall could perhaps have been an access bend). Hopefully this can be rodded up to the stack through the toilet pans. Down the stack will hopefully be roddable through the two 90 bends (though the grey one is a tight bend) having removed the AAV and if not the by pulling out both bends as well as the AAV.

Here's how it ended up I snaked it round some Hep2O so four bends in the end. I heated the pipe more locally than I would have liked so I can see it's thinned a fair bit at a couple of the bends. To squeeze the pipe section in it's ended up leaving the pipe quite taut. Hopefully that won't cause one of the joints to fail.

It's nothing special and had to get an angle that shows it clearer. The 32mm pipe on the right is above screed and the 40mm pipe on the left is below screed. To have a consistent drop (18mm / metre) that follows the left hand pipe requires a 24mm vertical offset. There are other places I am likely to need a small offset, so it's not just about this. I hoped someone might say Brand X sell a small S-bend offset part.

I know I can happily make any offsets I need above 60mm by using two 32mm solvent weld 135° (45°) Bends. But as you can see below, you can't go below 59mm. Are the only two ways to make a smaller offset that 60mm one of these two approaches: heat bend a straight length of abs pipe filled with sand using a heat gun use a length of flexible pipe

Sorry if it's a basic question, but I'm aware of two types of reducer and am unclear under which circumstances you use which. https://www.floplast.co.uk/product/level-invert-reducer https://www.floplast.co.uk/product/reducer-3

No basketball players here. I'm 6'2" and the boss is about 5'7".

I'm not sure if I have ever used one of these, but I think they are designed for better accessibility. The rim height is higher (e.g. 395mm vs 465mm). That's not currently a requirement for us in our en-suite, but is it generally a good idea? They have another advantages vs box outs as the pan's inlet is higher. Below are the two options for the same model. I also notice the Comfort Height Pan is 522mm long vs 495mm standard.

Odds of both toilets being flushed at the same time should be reasonably low, even if I'm cooking Sending it up inside a stud wall is a nice approach, but this is near only blockwork walls.

I'm a fan of laser levels so you can do this with one too. The laser shines a level plain so, with the laser set up in single position, as you move away from the house you should measure and increasing height between patio and laser beam.

Wow these sorts of thoughts can lead you to strange places. Looking at BS EN 12380 : 2002, the flow rate quoted by manufacturers is at a pressure drop of 250Pa. Also the valve must be open by 150Pa and have a measurable flow. 250Pa = 25mmH20 = 1inH20. Most 82mm AAVs have a flow rate of ~40L/s according to BS EN 12380 : 2002. Using this duct calculator, 40L/s creates a pressure drop of 137Pa/m of 50mm ID pipe (only 18Pa/m for 82mm OD = 75mm ID pipe). I hoped the pressure drop would be much much less than that across the AAV itself, but it isn't. Hmm. It is worth noting though that the resistance of two 50mm pipes across 2m is the same as one 50mm pipe across 1m. I have seen some say that running two 50mm pipes to AAV is OK. I could get away with a section of 50mm ID pipe only about 0.4m long before swapping to 82mm pipe.

@Nickfromwales and others have kindly pointed out on thread(s) the minimum size requirements for AAV on 110mm stacks, which to summarise I understand as 1no. 3" vent or 2no. 2" vents. However, what about the pipe size leading to the AAV? Can you have a 50mm pipe which steps up to 82mm where the AAV is? The area of a 50mm pipe is about 2,000mm2 and an 82mm valve would have to have a stroke of 7.6mm to open up an equal size area [1]. How big is the stroke on these AAVs? If less, should be OK to use 50mm pipe. In theory 😃. Am I on to something? [1] That area would in the form of a slot be more restrictive than a round opening by a good amount, but let's ignore that as the pipe has length.

It's worth noting that the 32mm, 56mm and 82mm Durgo brand AAVs are A1 but the 110mm one isn't: https://www.hunterplastics.co.uk/media/1791/bba-durgo-certificate-06-4325.pdf

I can >=200mm above where they join the stack but not so easily>=200mm above the basin overflow which is a fair bit higher

It's occurred to me that the shower wouldn't be an overflow point as its trap will probably have a non-return valve. I think I'd want the AAV to be higher than the bath's plug hole [1] and probably higher than the toilet pan's rim [2]. [1] The basin joins the same branch as the bath that then joins the stack below the toilets branch. I think that means the basin can't overflow the AAV without already starting to fill the bath. [2] A blockage between where the basin branch joins the stack and the toilets branch joining the stack would overflow the toilet pan before reaching the level of the AAV.

Thanks @Marvin That is guidance for Polyvalve which may not be a A1 rated which apparently does allow installation below the spill-over level. See below from Floplast. Annoyingly, their picture doesn't actually show it lower than the basin, but the Minimum 200mm and text makes it reasonably clear. Even if it is an OK approach, I would still have to convince the BCO though. "11.5 FloPlast AVE100, AV110, AF110 and AX110 valves must be fitted in a vertical position 200 mm above the highest branch connection (see Figure 3). As FloPlast valves are A1 designated to BS EN 12380-1: 2002 it is possible to locate them below the lowest reservoir being vented." "1.8 FloPlast AAV’s are designated A1 in accordance with BS EN 12380: 2002 and can be fitted below the flood level of connected appliances, in air temperatures between -20°C and 60°C." https://www.floplast.co.uk/uploads/related-documents/BUsohExhe3Mqhq6jYrAqs9kLySHpgjrtGe5hGvjo.pdf

I have a soil stack in a bathroom which is taking waste from a bath, shower, two toilets (one coming through the wall) and a basin. I know that AAVs are supposed to be mounted >=200mm higher than the highest entry to the stack which I can do where I want to put it in a boxout next to the toilet. However, does it need to be 200mm above the highest entry point to the waste system that feeds the stack? That is the basin which is higher than where I want to fit the AAV. In terms of the system filling up, it would overflow into the shower and bath before hitting the level of the AAV so does that mean it's OK to have the AAV where I am proposing?

Following further investigation, I am pretty sure it is the deflection head. The metal deep track rubbing on the OSB I think. Below is a video. You can hear the squeak as I pull and push on the screw through the deep track. For extra detail, the screw is from attaching a piece of batten that clamps the acoustic partition roll so no way that itself is the source of the noise. I can also push directly on the track having pulled it up using the screw and get the squeak. The amount of movement is tiny as I can't see it by eye. As viewed, the wall has a single skin of 15mm plasterboard at the top of screen and 11mm SterlingOSB + 15mm plasterboard on the other side (bottom of screen). The room on the bottom of screen is a bathroom, hence the OSB as well as the green VCL. I don't think I can do anything about this unfortunately. The wall downstairs is now plastered. I don't have access from above all the way along the deflection head and it's not like I could glue that anyway as it would stop it from doing its job. Rats! I guess I'm stuck with it. I'll get the wife to wobble around on top of it and listen in the rooms below to see if I can hear it. At least the OSB is on the bathroom side and so that's less annoying than the bedroom side. but that's on the hope that the APR and plasterboard deadens the sound. VID-20240611-WA0000.mp4

Do you think yours was the joists rubbing together or the joist rubbing on the hanger/nail? I'm not sure I could do that as I think the nails will have opened up holes in the timber too large for the screws to grip properly I wondered about dribbling PVA glue into the area a few times and see if that binds everything up

It's prior to boarding that area so definitely something to do with joists, noggins or wall. The two plies of the 2-ply joist are nailed together. Can't feel any relative movement between the plies. I guess it's easy to add some screws as well so I'll try that, but I'd be surprised if it works.

I am boarding out our loft space which is to be one large room. There is one annoying joist pair (actually bottom chord or RIR truss). If I move my weight from one to the other there is a squeak sound. If I move my weight from a neighbouring joists on the other side onto each there isn't a squeak. There is a wall (C-studs, one side with just plasterboard and one side with OSB and plasterboard) under this area. I think it is under the 2-ply joist that forms half of the squeaking pair. The wall has a 10mm deflection head. Below is a diagram with the joists in blue (one is a 2-ply), noggins in pink, perpendicular joist in yellow attached with a hanger (grey) and wall in orange. I am struggling to work out where the squeak is coming from and would like to address it before boarding over. Once the boards are down in this area I figure there'll be nothing I can do to stop the squeak. I wondered if it was the deflection head, but if it is that then I would expect there to be a squeak rocking my weight between 'joists' 3 and 4 as well. Actually, thinking about it again, 'joist' 4 is actually noggins off the yellow joists which run off joist 3 so maintain a load on 3. The noggins between joists 2 and 3 look sturdy. The hangers are extensively nailed (yellow joists pre nailed to 2-ply joist before hangers fitted). Any suggestions as to how I should hunt down the source of the squeak. I have had someone listen quite closely whilst I rock back and forwards but we haven't worked out where it's coming from. Section view: Here's a plan view:

Key factors for sure and any lateral force needs to first overcome the compressive force to start putting joints into tension. But not just mass and gravity. The narrower the footprint the easier it is to push over. Edge and top restraints would be key. Another aspect is the allowed deviation of 8mm is 16% of a 50mm block width. 50mm Thermalite block looks to only weight 3kg so that's just 72kg plus mortar per m of wall which is comparable to my weight.

Use 100mm blocks. Lots of suppliers selling 75mm blocks for more than 100mm blocks. Higher strength blocks are more expensive so that's a factor. The 'stiffness' of any membrane goes with the cube of its thickness so a 75mm wall is massively weaker against lateral forces. Cost - 100mm better Sound - 100mm better Strength - 100mm better Giving back 25mm of room - 75mm better I'm not sure I'd want to lean against a wall made of 50mm blocks.