Gradient on the discharge piping from a Saniflo

[Rogeranerley]

Hi

I'm planning to install a sanislim. When I first contacted the company a while back, they just mentioned that I should ensure any 'horizontal' discharge piping had a slight gradient. So, several years ago in preparation for it, I laid in a run of 22mm copper under the floor of another room.

I've now discovered the gradient should have been a min of 1:100 whereas the pre-installed piping is only at 1:150.

As I've faced difficulties finding a good connection between plastic and copper, I've already decided to pull the copper out through the exterior wall and replace it with 32mm solvent weld threaded back through the floor void.

In order to avoid lifting floor boards in the adjoining room, my question: is a drop of 1:150 in 32mm the equivalent of 1:100 in 22mm? I understand that this principal applies in larger diameter waste piping 1:150 for 150mm as compared with 1:80 for 110mm.

The pipe run will now be all in 32mm from the top of the unit turning almost immediately down into the floor void and run 'horizontally' some 11 metres to the main stack.

Many thanks

 

[onecog]

Seeing as you are not having much of an uplift you should be ok with 32mm and slow bends.Try it and see

 

[Agile]

I wonder why you ever put 22 mm as thats too small anyway. Also expensive in copper.

Whilst the fall is one thing getting no sag when full of heavy water in plastic pipes is another!

Maintaining the correct slope under a floor without top access for fitting supports would sound difficult.

Tony

 

[Hugh Jaleak]

It is imperative to get it right the first time, the pump will clear the effluent from the unit, up to a certain height, but it then relies on gravity to some degree to flow to the discharge point. Threading the pipe through under the floor is a recipe for disaster, plastic pipe will naturally flex to some degree, and without adequate support I cannot see how you would be able to guarantee a suitable fall, let alone avoid the natural 'sag' of the pipe. Any low points are going to allow waste to accumulate with I think, eventual inevitable consequences.....

If it blocks up, or the pump is struggling to shift the contents of the unit after someone has been busy in the bathroom, then messing about with a pipe that is now full of minced human waste is not a job for the faint hearted.

 

[Rogeranerley]

Thanks for all replies so far.

I'm lucky in that the original lath & plaster ceiling below the now floored out room has been removed and with be replaced when the pipe run is installed. I'm having to increase the original bore holes made for the 22mm to 38mm through the 6x3" joists which stretch 6 feet max across the floored room and will restrengthen these with 2x2" angle iron (from local scrap merchant) latched into the wall. The joists are centred at 15" max, giving me a firm support every 12 inches, which should solve any sag issues.

As there's almost no lift involved, I'm assuming the pressure from the unit's pump will push its contents the 11 metres into the main stack, but, if anyone can give me a technical answer on what the equivalent gradient in 32mm is for 1:100 22mm, it would help me sleep a little easier at night.

As for 22mm, that's what Saniflo state, they just forgot to mention it should be in plastic....and at 1:100 when I phoned!

 

[Hugh Jaleak]

1:100 is the gradient, the size of pipe is irrelevant!

 

[Rogeranerley]

Thanks Hugh

What I'm puzzling over is whether the extra 45% (10mm) diameter permits a more shallow gradient as is allowed with larger diameter pipe such as 150mm soil pipe able to run at 1:150 as opposed to 110mm being specified at 1:80 (or 100 in exceptional circumstances).

 

[Agile]

Soil pipe is designed to operate with solids which need a lesser fall!

Brunel Uni used to have a demonstration with clear plastic tube showing that at a steeper angle the solids are not moved! Its rather counter intuitive.

You are right that they will operate down to 22 mm which would normally be in plastic but thats a minimum size and the larger is best when any significant distance is involved.

Tony

 

[bolshy]

If you install a sanislim it should pump at the designed gradient (1:100) to a distance of 40 metres using 22mm bore pipe. If this fall is increased to 1:33, according to manu's specs, it should pump out to any distance. Decreasing the gradient, who knows? You have to remember how much volume and therefore weight the unit may be trying to push down a larger bore pipe, which will almost certainly be 2 to 3 times as much with the bore increase from 22mm to 32mm. Slow bends, 1:100 gradient, 22mm bore, should be problem free. You are just going to have to try it and see.

 

[Rogeranerley]

Thanks for all your help so far guys.

I'm still working on getting the gradient closer to 1:100. Also, I've had a thought on building in a servicing option for any sludge/blockage issues if I have to settle for 150.

Saniflo seem OK in their specification on having a drain tap fitted at the base of the lift when discharging vertically in 22mm, so seem confident such fittings offer low potential for sludge build up.

As I'm discharging horizontally in 32mm, and as the pipe work runs through the upstairs corridor, my thoughts are to install a solvent T piece + Inspection cap (Osma parts 4M190 & 4M292). This would allow me to set a removable board in the corridor flooring, enabling me to have an inspection & rodding point on the horizontal. The T piece would need to be set in the correct 'flow' direction with cap in the upper position

Can anyone see a problem with this idea?

 

[Rogeranerley]

Opps! Should have said the T piece is 4M190

 

[Hugh Jaleak]

A very sensible idea, as long as its all glued together securely! Although I doubt it'll do your decor any favours should you need to use it..... 45 deg junction may be better, would make for easier access to get a snake or similar along the run. If not already planned, i'd fit a 'T' to the end of the run where it emerges before joining the stack, with a rodding eye there to give access back up the run internally. Between the two rodding eyes you should be able to clean out the run without getting too plastered.....

I dont think the discharge pipework, fitted correctly suffers too much with sludge build up, the major issue arises when the unit itself packs up. (Not if - when!). This often can leave a pipe full of minced waste, all waiting to make an exit out the same way it went in.... Removing the unit for inspection without disconnecting it first is usually not possible.....

 

[Rogeranerley]

Thanks again Hugh

The 45 deg junction sounds a better idea on the horizontal.

I like the idea of an external rodding eye on the 90 deg turn to the stack (1 y piece glued to a 135 deg bend, or would 1 T piece be OK?) but wonder whether the inspection cap area might gather sludge and eventually block the pipe.

What do you think?

 

[Hugh Jaleak]

I'd use a 90 T on the outside, quite a common fitment on waste pipes from sinks etc. It may pay to angle it down, then use a 45 or 90 bend (not an elbow) to the stack to encourage the flow to take an easier path. Flow should be a fairly high water content anyway.

Bear in mind these macerators will only handle human waste and toilet tissue, anything else is asking for big problems..... Golden rule, nothing to go through the macerator that hasn't been through you, other than the toilet tissue!

 

[Rogeranerley]

Thanks Hugh....I'll have your last line printed on the toilet seat!!