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How to fix leaking rainwater tank downpipes & overflow?

Good morning!

I just moved to a new house and found that the Rainwater tank is leaking water from the downpipes but also the overflow. It appears that has moved slightly over the years causing a minor misalignment (probably 10-15mm at the top). It doesn't look like anything major but I don't want these leaks to contribute further and cause additional erosion next to the slab (which then will make it worse over the years).

Problem 1 - Down pipes. They are a bit off as per the picture. Is there any efficient solution to create a flexible pipe towards the tank to avoid further pipe re adjustment on the wall? I would say they are about 15mm off (tank tilting few degrees off the building line)

Problem 2 - Overflow. The same tilting has cause the overflow pipe to dislodge. The photo below shows the water scaping under the overflow pipe

Additionally, is there any good DIY solution to monitor the level of the tank.

Regards,

Sergio

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Comments

AlanM52

Hi @maccifo,

Likely PVC cement was used on most of the connections.

Screenshot 2026-01-26 154334.jpg

For that one there should be enough flex so it does engage.

Should you use PVA cement for that?

Personally I never cement any direct water tank connections because down the track I don't want to find myself in a position where I am flame licking around the connection and waiting for the cement to soften.

Screenshot 2026-01-26 161950.jpg

Same thing for that one.

Screenshot 2026-01-26 162105.jpg

For that one.

Screenshot 2026-01-26 154732.jpg

Fittings like that should do the job.

Screenshot 2026-01-26 154846.jpg

In conjunction with that.

With regard to tank water level here is what I did and I can't remember the exact details because that was back around 2006.

T-piece on the tank outlet with adaptor for the ball valve then another adaptor to connect (and this I remember) Pope 13mm x 5m Clear Vinyl Tubing .

The tubing was cut near the top of the tank and secured with a pan head screw directly into the tank.

Looking ahead I figured the tubing would become messed up on the inside and discolored on the outside and that was the case so when needed I to change I simply turned off the water (ball valve handle at 90°) and changed to tubing.

Around that time smart home automation was taking off but I never bothered.

You of course now have many smart options to monitor water level via a phone app.

Come back if you need more info about that.

Cheers

MitchellMc

@AlanM52 has already given some excellent advice, @maccifo. The first thing to check is whether the downpipes can actually be moved back into position or if they are now too far out of alignment to reach. The best approach is usually to extend the solid pipework so it meets the tank properly and then secure it with a suitable gutter silicone to hold it in place.

For the overflow, it looks like it may simply have come loose from its fitting. Check whether it was originally glued in with sealant. Any old sealant should be removed before resealing the joint, then you can reposition the pipe and fix it in place with fresh silicone.

Using flexible pipework in this situation is generally not practical because the space is too tight for a short flexible section to bend without stress. Extending the solid pipes slightly is usually the simplest and most reliable solution. This way, both the downpipes and overflow can be properly aligned, stop leaking, and avoid any further erosion around the slab.

Please let me know if you have any questions.

Mitchell

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