Grundfos Macerator

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Not sure if this is the right place to post this, so sorry if it's not.

I've had a grundfos macerator in my bathrrom since just after I moved in (about 5 years.) It's never worked right, and it eventually went kaput last week. So I replaced it with a newer version - a Sololift WC. But I still have the same problem, which is that the pump sometimes works ok, but sometimes can't pump the water away for a long time, then it eventually gets over the blockge or whatever and clears.
The setup is as follows: from the macerator, there's a 90 degree connector coming out of the side and then going vertially upwards (supplied by grundfos). Then, to connect to the old system, I have another 90 degree bend with a reducer to 22mm copper pipe, which has a short (400mm) horizontal run before turning vertically and going up about 2.4m through the ceiling. In the loft, the pipe turns through 90 again to run horizontally (with a slight drop) for about 8m. Then it comes out of the wall, turns through 90 degrees again and drops vertically for one storey before joining the 32mm vertical pipie that drains the sink and bath which travel vertically into the main waste.

So, I think either the pipework's too long and narrow and the pump can't cope (although it ought to be able to) or I'm getting syphoning causing airlocks. Would a none return valve in the vertical copper pipe in the bathroom help? Or one of these to equalise the pressure http://www.plumbworld.co.uk/442-1788 Or maybe increasing the pipe bore to 32mm (in which case where do I get a fitting for that) after the vertical rise?

Any other ideas from someone who knows?

Cheers.



PS, When we first moved in there was a Saniflo and that was even worse. Died after about a month. The people who installed the bathroom in our house before us decided it would be a good idea to put it somewhere where there was no outside wall. They had the bath and sink going into it too, which meant that once we had raw sewage coming up through the bath. Nice. Luckily, there's an outside wall close enough to enable us to have rerouted the bath and sink under the floor. But it's too long a distance to get the correct fall for the toilet. I would avoid these things like the plague from now on, but unfortunately I don't have a choice, other than moving stuff about, and it's a bit late for that. I just want to get it to work properly so we can sell the house.

PPS sorry for the long post.
 
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Macerators tend to be a nightmare if fed the wrong things or if wrongly installed (or, worst case, if the month has a vowel in it!).

It's a pity you junked the Saniflo. Most plumbers won't touch them (for obvious reasons) BUT the manufacturers have in-house engineers who can fix them or at least explain why they don't work. They must be heroes!

Maybe Grundfos can offer help.
 
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This is the first time that I have heard of a problem with a Grunfoss.

They have been pushing their macerators for a few years.

It vsounds to me as if there is a problem with the installation rather than with the unit.

Let us know how they deal with the problem.

Tony
 
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I may have read you wrong but did you say the outlet had two separate 'up' runs?? This is generally a no no. Only one up run is allowed and then everything else has to be horizontal ( with a slight fall ) or downward drops. I know this is true of Saniflows - we fit them a lot. Cant vouch for Grunfoss though.

Also, is the one storey drop from the loft necessary? We often go into the soil stack as it vents out through the roof or past the soffit and fascia. This would help any siphonage issues.
 
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The drop from the loft doesn't go into the main soil stack, it goes into another inlet to the main waste done specifically for the bathroom (moved from the original one which has been sealed and is too far to get to.) They really did a strange job on this originally, but I wasn't here then. The two vertcals are because the fitting that comes with the unit is l shaped - out the side then up - and the vertical pipe that's already there is about two feet away. hence, vertical, horizontal, vertical.

The only trouble with calling grundfos is that they didn't install it and they want £150 callout.
 
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An anti siphoning loop is what should be used preferably at the highest
point as the pipe goes through the loft to the outside wall before going
down the outside of the house wall.This will keep more of the pipework full
and so a more consistent back pressure on the Sololift.

The Anti Siphon loop should always be at the highest point of the discharge
circuit. It is no good doing this at the waste stack connection unless the
loop height goes above the Sololift discharge connection.

The customer could try increasing the pipework size by a couple of sizes
that runs down the outside of the house and where it connects to the waste
stack. This can break the siphon by allowing air to inrush from the waste
stack connection as the pipework has more of a water fall effect than plug
flow occurring in it due to the larger size.

If the unit does siphon then the problem as experienced occurs as air is
drawn in via the pump and then air locks and even though the unit is filled
with water the pump does nothing due to loss of prime (air lock) locally.

I trust the above helps?

Kind regards
Paul Wightman
Applications Support Engineer
Grundfos Pumps GB Ltd
Tel: 01525 775328
Email: pwightman@grundfos.com
 
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spark29uk said:
Nice. one. Where do I get an Anti Siphon Loop?

You make one with fittings

I would simply increase the pipe size through the roof to the stack so the pipe cannot fill with water
 
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Ok,

Firstly, thanks for all the help.

So, I finally sorted it. And like most problems, the solution was very very simple, it just took some finding. I tried putting in an anti siphon loop in the loft. It did very little. So then I just swapped the vertical drop from the loft to the waste from 22mm to 40mm pipe. Problem solved. I guess it can't siphon because the larger bore breaks the vacuum well above the level of the macerator.

So thanks again for all the info.

I hope this helps someone else one day.


Cheers
 

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