Sludge in rain water tank

To give you an idea of tank deflection when full, have a look at the first photo in the post that I have linked below.

viewtopic.php?p=1146540#p1146540

The hose is a balance line between two 'CAMEL TANKS' as used in the Gympie rainwater harvesting thread. There were 4 tanks in all, CAMEL TANKS apparently called it a design feature when told of the problem!!!

Re what I was told about root inhibitor in DWV pipes, I think the person who told me that was mistaken. I spoke today to people from 2 pipe manufacturers, and they both said they don’t put root inhibitor in, and the ring of blue colour I saw would have been because they often use reground/recycled pipe sandwiched between an inner and outer layer of virgin PVC, and so the sandwich layer is coloured by whatever colour the reground pipe was (eg blue for mains water pipes).

I got the impression from one manufacturer that there’s nothing in the formulation of their DWV pipes that would be harmful, as apart from the foam and/or regrind, the different types of pipes are made of the same stuff. But because they don’t get their DWV pipes tested to see if they comply with AS4020, they can’t say they do.

But the rep from the other manufacturer said he’d heard of people getting knocked back when they were inspected because they’d used DWV instead of pressure pipe for downpipes into rainwater tanks. Has anyone else heard of this happening?

I agree but it was a good story.


No, but in plumbing, anything is possible and it is in line with what the regulations state. It's a ridiculous situation.

Save H2O, I was just reading your article in Renew magazine (#127), in which you said to leave enough room between the downpipe and the mesh on the leaf diverter to prevent blockages.

We're planning to cut the downpipe diagonally to make it parallel to the top of the leaf diverter (Rain Harvesting's "Leaf Eater Original with Clean Shield"), and to leave a 50mm vertical space between them (which Rain Harvesting advised). Do you think this is enough space to minimise blockages (and also minimize water loss through splashing off the leaf diverter?

Is there a minimum length of downpipe (between the bottom of the gutter and the leaf diverter) that we should have? (I'm wondering if the water would be more turbulent (because of turning 90 deg. at the end of the gutter) in a short piece of downpipe, and if so, whether this could cause more splashing out of the leaf diverter?)

I'm thinking of having 106mm of downpipe at the short side of the diagonal cut (198mm at the long side). Would longer be better? (Although the longer it is , the shorter our First Flush Diverter will become, which is already 4 times shorter than you recommend (2.6m of 100mm DWV for 90sq m of roof)!

I always recommend to people that they leave enough gap between the bottom of the downpipe and the mesh so that anything that can pass through the bottom of the gutter pop will also discharge from the downpipe. Note that the gutter pop's lower orifice is smaller than the downpipe, for example, the bottom of a 100mm x 50mm downpipe pop will usually be 92mm x 42mm.

I do not consider a 50mm gap between a downpipe and the mesh to be sufficient for most downpipes, particularly a PVC-u 90mm or 100mm round downpipe.

Downpipes are usually installed close to the mesh to stop wind blowing falling water to atmosphere. High sides prevent yield loss caused by wind but not all leaf diverters incorporate this.

During lighter rainfall, a lot of water travels down the downpipe's inner wall that is furthest away from the house and the reason for this is because the section of downpipe that is sloped towards the house wall transfers water by surface adhesion to the downpipe's outside wall.



The above photo shows several points of interest.

1. The downpipe has been cut diagonally...imagine the affect of wind on falling water were it not!

2. The downpipe slopes outward due to the 88 degree fitting and the horizontal slope under the eave. The longer the pipe, the greater the distance the discharge will be from the wall (in most instances) and the closer to the leaf diverter's furthest edge the water will land.

3. Water doesn't fall directly downwards from a downpipe, it splays out slightly due to the thickness of the pipe's wall combining with surface adhesion to arc the water outwards.

Re the downpipe length, the longer it is, the faster the water flows but it isn't a real issue with metal mesh.

A few notes about leaf diverters and what to look for.

If you have a wet system, make sure that the leaf diverter has mosquito proof mesh (less than 1mm/1,000 micron filtration) and no other entry points.

It is recognised that a minimum 60 degree filter angle is the minimum requirement for debris shedding but water will run over a steep small aperture wire mesh surface, the reason most leaf diverter mesh filters have lesser angles.

Make sure that debris can fall off the filter mesh and that there are no areas on the surface that retain debris.

Make sure that the reservoir completely drains and does not retain water and debris.

Make sure that the bottom drain pipe provides a firm secure seal with stormwater pipe fittings.

High sides will prevent wind induced yield losses.

Thanks for your reply SaveH2O.

You said "I do not consider a 50mm gap between a downpipe and the mesh to be sufficient for most downpipes, particularly a PVC-u 90mm or 100mm round downpipe."

We'll be using 100mm uPVC downpipe coming straight down vertically from the gutter outlet. The leaf diverters we're using look very much like the one in your photo. The straight vertical wall at the back of the leaf diverters is 55mm high. So if we have the vertical distance between the diagonal bottom of the downpipe and the mesh on the leaf diverter more than 55mm, there will be space for the wind to blow the water aside. It's hard to know which would be worse - (hopefully only occasional) blockages because of too short a distance between the downpipe and the leaf diverter, or (possibly frequent) water loss and splashing where it might be a nuisance because of too big a distance. What's your opinion?

The leaf diverter and first flush diverter below it will be on a pole, not on the wall of the house.

We thought of having the downpipe (ie the top end of its slope) hard up against the back vertical wall of the leaf diverter, and about 50mm of downpipe between the bottom of the gutter outlet (a UPVC one that fits under the gutter) and the highest bit of the diagonally cut downpipe.

Could you please clarify a couple things from your post?

"During lighter rainfall, a lot of water travels down the downpipe's inner wall that is furthest away from the house and the reason for this is because the section of downpipe that is sloped towards the house wall transfers water by surface adhesion to the downpipe's outside wall." By "outside wall", do you mean the outer surface of the pipe, or the inside surface of the longer bit of pipe further from the house?

"Make sure that the reservoir completely drains and does not retain water and debris." Which reservoir?

It really depends on your own situation. If you were reliant on harvested rainwater for potable use, you would be concerned about any yield loss and would almost certainly opt to have the pipe's outlet closer to the mesh as most do and monitor the diverter for large objects causing blockages. If yield loss was not a concern, then nuisance value and the visual effect may be.

The way the current crop of leaf diverters are designed, the onus is on the owner (or installer) as to how close to the mesh the downpipe is fitted. I have seen many leaf diverters with blockages between the mesh and the bottom of the downpipe and many leaf diverters are installed in situations where climbing a ladder to clean them presents a considerable safety hazzard.


The pipe's inside wall that is furthest from the house.

In my previous post, perhaps I should have written "During lighter rainfall, a lot of water travels down the downpipe's inner wall that is furthest away from the house and the reason for this is because the section of downpipe under the eave that is sloped towards the house wall transfers water by surface adhesion to the vertical section of the downpipe's outside wall."

If you look at the photo in the previous post, you will understand what I mean.


The leaf diverter's reservoir under the mesh. Believe it or not, not all leaf diverters completely drain! This is why you sometimes see weeds growing inside leaf diverters.

[quote="SaveH2O"]

It is also easy to install a cheap and simple DIY sediment trap into the wet system's pipe work. The trap is installed 4-5 metres past an elbow or tee as it must be in a non turbulent section of pipe to capture settled bed load. As you can see in the diagram below, when the very slow travelling bed load reaches the opening in the 45 degree junction, it simply drops down and is later flushed through a reduced sized pipe at high velocity.



Hi SaveH2O, thius is interesting, but I'm not quite sure what you mean by the "flushed through a reduced sized pipe at high velocity" bit...

Firstly, you can only reduce the pipe size if you have leaf diverters fitted to the downpipes. This is to safeguard against a dead bird etc being washed into the wet system and then trapped by the smaller pipe.

The pipe immediately after the junction is reduced in size to minimise water loss and to reduce costs. Because the pipe is reduced in size, it flows with a higher velocity when drained than would a larger pipe.

The link below is a one year summary of a 4 tank system in QLD that has the sediment traps (2 x 100mm DWV pipes). The rain harvesting system is probably the best in the district.

viewtopic.php?p=1146540#p1146540

I've set up one of these sludge pipe systems here, but haven't reduced the size of the end of it, so just straight out of my 100mm pipes.

I'm amazed at the amount crap that sits down the bottom of these pipes, and so glad that I put them in.

The required first flush system that the council requires, to me is a waste of time, and I could really do without them.

Other than the last 500mm of my downpipes are under the ground, and most of that is mostly shaded anyhow.