Gravity fed or pumped chamber to drainage field?

[flanagaj]

I wanted to ask whether there are any merits in having a collection chamber after the sewage treatment plant, which collects and then periodically pumps the contents into the drainage field pipes quickly so that the waste water in dispersed around all of the perforated pipe.   Our initial plan was to simply allow the waste water from the STP to drain as and when it is required.  I know some STP systems do exactly this and others Graf do not.  The logic apparently, is that by pumping a large volume you will utilise all of the perforated pipe, where as, allowing it to trickle out, means that only the early section of the field is used.  Obviously, as time moves on the early section of the field will probably slowly start to silt up and the water will naturally travel further into the field.   So my reasoning on this one, is that overtime the net result is the same and the field would have the same lifespan.

Logic correct or flawed?

[Bonner]

Keep it simple, use gravity to do the job. The drainage field will balance itself over time. I would only use a pump if absolutely necessary.

[ProDave]

Definitely.  Our past house had a pump out of necessity as the drainage field was higher than the treatment plant.  The pump would last somewhere between 5 and 7 years before it burned out and needed replacing.  I was SO glad when our present house was given permission to discharge to the burn, no pump, no drainage field.

[saveasteading]

What comes out is liquid and looks almost clean. If you have a test chamber you will have the comfort of seeing, even testing,  this. A chamber is a good idea anyway.

What muck remains in the effluent will continue to break down in the soakaway.

A pump should be unnecessary and is another thing to go wrong. I wonder why a manufacturer has one included apart from draining uphill.

 

[Kelvin]

The Graf system discharges the water twice a day using the compressor ‘pump’ the water out of the tank into the drainage field which makes quite a loud bubbling noise so I wouldn’t want it right near the house. It also has a built in sampling chamber. 

Edited Monday at 10:36 by Kelvin

[crooksey]

Your logic is correct, but flawed in execution.

 

A correctly designed drainage field that matches the percolation rate of the ground (during the winter) and sized accordingly to building regs will have no issues dealing with an output from the graf style outlets (twice a day volumes).

[Kelvin]

Here’s video that explains how their air lift system works. As @crooksey says the Graf system would work perfectly well with no extra pumps in the tank. It’s all done from the compressor. 
 

 

[flanagaj]

2 hours ago, Kelvin said:

The Graf system discharges the water twice a day using the compressor ‘pump’ the water out of the tank into the drainage field which makes quite a loud bubbling noise so I wouldn’t want it right near the house. It also has a built in sampling chamber. 

Thanks.  I was unaware of this and thought it just tricked out as new effluent entered the tank.

[Kelvin]

3 minutes ago, flanagaj said:

Thanks.  I was unaware of this and thought it just tricked out as new effluent entered the tank.

It shouldn’t ever be that full that it could flow out. It’s quite a pronounced bubbling sound as it lifts the water up the pipe into the sampling chamber. I have an SVP after the tank (best practice Graf install) and that’s where the sound is loudest. 

[saveasteading]

2 hours ago, flanagaj said:

thought it just tricked out as new effluent entered the tank.

Anybody know a good reason for pumping it out. Gravity seldom fails so I like it.

 

2 hours ago, Kelvin said:

shouldn’t ever be that full that it could flow out.

Ditto. Always full for the chambers that work that way.

A big plus for me is that they will continue to work 90% ( well enough) if there is no power or the pump breaks

 

[Russell griffiths]

The water from our graff tank is clear and completely odourless, it’s not likely to bung up your drainage field 

unlike my other septic tank which is horrible. 

[Kelvin]

2 hours ago, Russell griffiths said:

The water from our graff tank is clear and completely odourless, it’s not likely to bung up your drainage field 

unlike my other septic tank which is horrible. 

It surprised me how clear it is. pH of 7 too. It’s likely better quality than the rainwater going into our other drainage field. 

[saveasteading]

46 minutes ago, Kelvin said:

better quality than the rainwater

For fertiliser yes.

[Kelvin]

I have a full water testing kit. I might run a sample through it.