Backflow from loft - Macerator issues

[MJB]

Here's the scoop;

ensuite bathroom on 2nd floor with shower, basin and toilet.
Lomac 3000 macerator handles all this.
Pumps vertically about 10ft then horizontally about 30ft (pump is well capable of this).

2 problems;
1. Whilst showering the pump does not keep up with the water level so you end up ankle deep in water and cutting the shower short.
Once the shower starts the pump kicks in about 12 seconds into the shower time, great, then about 12 seconds later it kicks in again, beauty, but then there is about a 50 second wait before it kicks in again, then 12 seconds, then 12 seconds, then 50 seconds and so on.
It's these 50 second intervals that are the problem (I think).
During the 50 second interval the water all comes running back down the discharge pipe out of the loft and back into the macerator, sounds a bit like a waterfall, especially at night or when it's quiet.
I'm sure it's running back into the macerator, even though there is a check valve built into it. I pulled it apart and felt the valve with my finger, it seemed to be closing off OK.
The plumbers that installed this also say they installed a check valve somewhere in the vertical run of the pipe, yep, somewhere in the wall.

2. Problem 2 is related to problem 1, i.e everytime you flush the loo, it too all runs back into the macerator. Some waste gets pumped out in both cases as I have heard it from outside where the macerator pipe meets the main soil pipe.

It just seems to me that if it wasn't for the water running back down into the macerator then the macerator could just keep pumping every 12 seconds and keep the shower free from water. The backflow of water is keeping the macerator 'busy' and not allowing to do it's job for around 50 seconds.

I assume the check valve in the wall is faulty? and perhaps the one in the macerator? I'm sure I can hear the backflow going back into the macerator but it may just be the pipe filling up....

I don't want to rip the wall apart, what about a check valve where vertical meets horizontal? single or double CV? The pipe they have used is pvc, what CV do I need?

Also, just to confuse things even more....I can put the shower head into the basin and turn it full on, it never over flows, only the shower tray does. (the backflow thing still happens though but the macerator kicks in more often with the basin, about every 8 seconds then a 30 sec pause).

Thanks in advance to all.

MJB.

 

[chrishutt]

An interesting problem, at least. I wonder if the alleged second check valve buried in the wall might be the problem, not merely because it doesn't appear to do it's job, but because it's actually causing a lot of resistance to pumped flow.

Burying a check valve in the wall is plain stupid, so I would want to check if it is there, then extricate it or by-pass it. If you can access one end of the vertical run, you could feed a smaller tube or cable down until it hits the check valve (or not). This would at least confirm its presence and give the position in the wall. Or more probably show that there isn't a check valve there at all.

You can probably get a replacement check valve for the macerator from the manufacturers, which should be sufficient. Adding a second one may cause more problems than it solves.

 

[Paul Barker]

sell the house.

 

[Newboy]

Given the difference in performance between the basin and the shower wastes it might be a good idea to check the shower trap and waste and how it connects into the rest of the waste pipework to the pump

 

[MJB]

Thanks for the replies, funnily enough we are in the process of seeling the house!
Also, it did work fine some months ago, which is why I think the check valve(s) are the problem here.
Why the hell would it work twice (i.e every 12 secs) then all run back? If the valves were shot would it not run back every time?

Cheers again.

MJB
+++++++++++++++++++++++++++++++++++++++++++++
So if I was to put in another CV where the vertical meets the horizontal in the loft, should it be a double or a single?

Cheers.

MOD

please use the edit button

 

[kevplumb]

use a hepVo valve less restriction

 

[MJB]

Thanks Kev, do these act like a non return valve?

 

[kevplumb]

yes and a trap

 

[MJB]

Cheers Kev,

This will have to go in the loft on the horizontal, is this OK?
The only backflow then will be what's in the vertical, which will reduce it by about 75%....... and possibly leave my ankles slightly drier.

Can I have a HepVo up in the loft between 10ft of vertical 25mm pvc and 20ft of horizontal 25mm pvc?

 

[Paul Barker]

Yes they're marvelous devices, you can put them in horisontal runs, the picture shows the two types of connector you need for one end (which is designed to fit basin waste outlet, so needs conversion) the other end fits standard waste pipe.

If your pipework is solvent weld, which it ought to be, then because these are compression fittings they will go on. The unit is about 10 quid not sure how much the fittings are probably 3 or 4.

I like them in basin pedestals because they fit in neatly.

I hate macerators and refuse to go out to them.

 

[MJB]

Thanks Paul,

Sounds great, which pivture would you be referring to?
The one on plumworld?
http://www.plumbworld.co.uk/442-1788