Waste trap in concrete

[DIY Max]

Hi all, we are replacing a downstairs shower (whole room refit). The old tray was a whopping 20cm height from the floor. The waste outlet in the pic is 3 inches from the floor. The pipe comes outside just above the DPC. Our installer wants to dig and bury the new waste trap/pipe etc in concrete, tank etc and feed the waste into the main drainage system underground somehow. He has assured us there will not be any issues at all with this method and no issue with leaks at all. I am not 100% convinced this is the best option. I initially thought a raised shower tray was the way to go with timber or a raiser kit. Could really do with some advice on options here thank you.

 

[richw]

Well, the trendy modern approach is a lower waste, so you can have a low-profile tray without a step. It's popular.

The plumbing is more practical with a raised tray, but you have the difficulty of supporting them. Chances are, it will flex, which isn't what you want.

 

[DIY Max]

Thanks Richw. Not too fussed on look necessarily but prefer the lower profile. More interested longer term durability and access if needed. Also if there is any kind of issue we just won't know unless it gets very bad etc.

 

[endecotp]

Show us what’s the other side of the wall.

 

[DIY Max]

Will take a pic. It is engineering bricks, DPC. There is also a gutter where the waste water was dropping into. Outlet pipe above DPC. There is also a main drain pipe underneath the room going into the manhole on the other side of the room. It is an extension built about 25 years ago.

 

[DIY Max]

 

[endecotp]

So he'll need to break out the concrete outside and replace the gully (???) with something else? A photo from further back would have helped more.

It's certainly doable, but might require skills some bathroom installers don't have. Maybe he has photos of other underground drain work that he has done that he can show you?

You may need building regs approval for this. Is it a combined sewer?

 

[DIY Max]

No from what he has explained, dig out a channel from inside the room and connect to the main soil pipe which is connected to the drain you can see in the pic. The drain actually runs back on itself underneath the room where it joins the toilet pipe and then onto the manhole. So basically a 40mm pipe to a main sewer pipe i think! It is connected yes. I will certainly request pics, that's a good suggestion thank you. The chap is very skilled but I am getting more concerned about the whole approach now so will need to have a serious discussion.

 

[DIY Max]

If we change plans and simply raise the tray, would it be better just using a riser kit or on to a bed of concrete or timber frame? Its a 1200 x 700 tray and we will also need to route the basin waste into the pipework as that is how it was previously with both water exiting through the one outlet as seen in the pic. Old tray was on bricks and mortar with a void in the middle but was only a 75 x 75 tray.

 

[denso13]

Have it on the floor and go with your installer's suggestions, they sound absolutely fine.

 

[DIY Max]

Thanks Denso. Will see over the next few days

 

[dilalio]

Level access tray is so much better if you do it.

 

[Notadecor8ter]

I've got a raised shower in my ensuite (late 90's build) with waste sitting about into the Soil stack. Refit will definitely be involving waste being dropped into the floor voids if it's possible.

Are plumbers becoming more confident with these newer techniques or could these had been done when properties were built way back when?

 

[DIY Max]

I've got a raised shower in my ensuite (late 90's build) with waste sitting about into the Soil stack. Refit will definitely be involving waste being dropped into the floor voids if it's possible.

Are plumbers becoming more confident with these newer techniques or could these had been done when properties were built way back when?

We have that method upstairs but have left access just under the waste. It is directly underneath our front porch/entry which is very handy for any issues in the future. But we have paused this current job as a number of other issues cropped up such as double boarding and using push fits in buried walls!

 

[dilalio]

Are plumbers becoming more confident with these newer techniques or could these had been done when properties were built way back when?

Plumbers install what has been chosen by others most times.
Way back when...
Low profile shower trays weren't available...
There were nowhere near the number of options available, as there are today. Lots of this is to do with the materials now available such as GRP and resin.