Water coming up near down pipe

Hi there. I have an issue with water coming up around a down pipe that goes into a concrete path. There are 3 downpipes along this path that lead to a water tank about 20 metres away, and I believe it is gravity fed. When there is a lot of rain over a few hours, water appears up around the down pipe, then from under the concrete next to the house. I have attached a video.

file:///var/mobile/Library/SMS/Attachments/d8/08/2666DB97-CB48-4BCF-928A-CEBB87F334AF/IMG_1524.HEIC

file:///var/mobile/Library/SMS/Attachments/8b/11/A5601013-2DA2-4AD9-A1C1-CA52049121AD/IMG_1224.MOV



We had a plumber out a few months back who put a camera down and found no issues, and suggested it was our neighbours pipes that were leaking, and as we are lower than them, it was coming out onto our side. Last week we had them out again to check her pipes and they could not find anything wrong with her side. Then they thought maybe in heavy rain where her path butts up against the retaining wall, water was seeping into the tap and seeping thru the wall, and under our path. He Josef her path down for a while with no water coming out on our side.
Then he tapped our down pipes, and said the water level was lower than it should be, so there must be a leak somewhere in our down pipe system.
Now they are offering me either having the down pipe run externally next to the retaining wall to see if
The problem is still occurs in heavy rain, Or, they can cut the concrete around the down pipe, drain it and put a camera there, or just replace that section.
I rang another plumber who thinks cameras are useless in this situation as it would be too dark and difficult to see a crack or split.
Does anyone have any idea if it is the down pipe or could it be the neighbours pipes? The house is only 3 years old, should be under warranty but I cannot get the original plumber out. It does not happen all the time. We had heavy rain yesterday for a couple of hours with no problem.

Can you fix the link thanks?

Write reply...
I can only seem to post a photo.

The photo tells a story but not being on site is obviously difficult.

Does the ground slope up to the tank and am I correct in assuming that the downpipe shown is the one furthest from the tank?

No, this is the middle down pipe.
There is one closer to the water tank. The water tank is about 20 metres away from the closer down pipe, and is a bit higher than this path at ground level.

I was wondering whether water was seeping along a sloped (pipe) trench and was seeping up at the end of the trench.

Can you put some strong food dye in a pail of water and tip it into that downpipe via the gutter pop? Because the tank's vertical riser and the 3 downpipes will all have the same water level prior to doing so, it will be the coloured water that emerges if a fitting is leaking at that downpipe.

I am assuming that whoever did the plumbing used flimsy 90mm pvc stormwater pipe all the way but can you check the size of the tank's vertical riser thanks. Stormwater 90mm will be 90mm outside diameter whereas DWV 100mm is 110mm outside diameter.

We could try the dyed water, but it doesn’t seem to seep out when we test it. I suspect the ground underneath needs to be sodden before any water appears above the concrete path.
I have another plumber coming to look at it next week.
I guess we need to decide to we pay to turn the down pipes into external ones, at a cost of about $1200. The during the winter we can see if the seeping has stopped. If it has, we then rip up the concrete path and replace the entire thing or search for the leak....

It will take a while for the coloured water to infiltrate the present water.

This test is to try to localise the problem area. The plumber who said that the cam may not pick up a small split is correct, the majority of leaks are from the fittings, not the pipes. A column of water exerts a pressure of 9.8 kPa per metre and even though the wet system has lost water level which proves it is leaking, the rate of loss may only be the equivalent of less than 1 drip every few seconds.

As a plumber and if it was my job to trouble shoot the issue these are the steps I would take before even contemplating to rip up concrete or if it was the neighbour.

1- Cut the storm water pipe feeding into the top of the tank, cut it on the vertical up the side of the tank near the top elbow.

2. Look down into this pipe and determine water level. If water is at the top then there is no leak on the system of pipes bringing storm water to the tank. If it is empty and the water level is below or level with the concrete then this confirms a leak on the system.

3. If no leak is confirmed of the feed in side of the storm water system then I would cut the vertical riser on the overflow pipe coming out of the tank. Once this is done I would run a substantial amount of water through to the overflow system to the street. If water eventually shows then this section has an issue.

That is what needs to be done before doing anything with concrete or cameras. And as said above, a camera is useless in a pipe full of water.

Thanks for that. I have a plumber coming out next week so will tell him to do that.

No worries. If he is any good at maintenance plumbing trouble shooting he will do that anyway. good luck.

Harly, you said in your opening post that the water in the wet system was lower than it should have been.

Also, tapping a pvc pipe is the easy way to tell where the water level is. Has it rained lately?

It poured on Monday in Adelaide, but there was no water seeping up. Prior to that rain, it has been dry for weeks. It has happened before where I expect it to seep up, but then if it rains the following day, then the seeping usually starts.
We had plumbers out a couple of weeks back that felt the water in the down pipes was lower than they should be. They said water was going into the tank, but I didn’t see them look at the level of the pipe feeding into the tank like mentioned above.
The plumber coming out next week is coming to look and decide where to start.

Are you sure this isn't a charged system ?

I don’t know, is that a gravity style system?

The water in the vertical riser will be the same level as in the downpipes. They can't be different levels relative to each other but the water in the downslope downpipes will of course be higher above ground. You would check the level in the riser, not the downpipes.

I'm still wondering whether the trench is serving as a conduit for upslope surface water but why it comes to the surface at the middle downpipe is strange. I did however see in the photo what appears to be a wet area upslope from the downpipe along the path/wall intersect. Is this right? If so, then I am wondering how the seal is along that intersect and whether rain falling against the wall is able to seep between the wall and the path.

Rain doesn’t hit the wall as the eave is about 80cm wide. Not a lot of water lands on the path as it is narrow, and the neighbours roof and gutter is quite close. The only time water ends up the path is in a downpour where water overflows over the gutter which doesn’t happen much.
Plumbers a couple of weeks back thought it could even be where the neighbours concrete path meets the retaining wall. They thought water could Seto through the gap, go down into the ground then under our path up next to the house.
I don’t think those plumbers really knew, and they just suggested to change the piping fo the down pipes run externally rather than into the ground to see if it still happens. If not, we know there is a leak somewhere in a down pipe, I don’t really want to do this as it would cost about $1500 to change over to external piping, then god knows how much to then rip up the path and redo the pipes.

They have considered a possibility which shows that they at least thought about it in a professional manner but situations like you have are invariably difficult to pinpoint. It is a solid possibility though.

One of the problems with a standard charged system is that the stormwater system is rerouted and even if you wanted to disconnect the rainwater tank, you would still have the expense and inconvenience of connecting the three downpipes to the water tank's subsurface drainage.

For now, all I can suggest in the short term is to monitor the water level in the tank's vertical riser because that will tell you for sure whether the wet system sump has a slow leak or not.

The downpipes appear to be 90mm pvc stormwater pipes, these hold 5.8 litres per metre (the internal diameter is 86.2mm). There are 3 DPs plus the riser that I assume is also 90mm pvc stormwater. This gives a total volume of 23.2 litres per vertical metre. One drop (not Apothecaries measure) per second is approximately 13.5 litres every 24 hours or 0.56 litres per hour. Even at this slow rate, the pipes would drop a bit more than 1 metre after 2 days. If the level does drop, you should be able to get an idea of the rate of leakage but sometimes the power of the Universe decides to deal a double whammy. Let's hope that it is a singular cause.

Thank you for that.
I have a question about the height of the water in the pipe leading into the tank. What should it be? Currently we only have a small amount of water left in the tank, about a 40cm height. The tank is about 2m high. I don’t know where it is sitting in that pipe, should it be at a consistent height?

You will almost certainly have a 'run of the mill' charged (wet) system that delivers water through an underground 'sump' to a vertical riser that discharges the water to the tank's top meshed inlet. The water level will be at the height of the riser's invert at the top elbow unless the installer has also foolishly fitted a first flush diverter near the top of the riser. If so, the water level will be at the lowest point of entry to the first flush pipe.

Additional information:

The photo below shows a woefully fitted overflow pipe on the left (no mitigation) and an equally woeful vertical riser on the right fitted with an equally woeful first flush diverter near the top. So...why are (1) the vertical riser and (2) the first flush diverter also woeful?

(1) The vertical riser allows mosquitoes to access the standing water because a flap valve cannot be fitted to a 45 degree elbow.
The flow path is archaic and ugly.

(2) The first flush capacity is too small (it probably holds about 6 litres) BUT in this situation, it actually wastes less water needlessly collected.
The first flush (the initial dirty roof wash) only fills with the standing settled water retained in the riser since it last rained while the first flush will still be in the downpipe(s) at the end of the wet system!