Replace cold water tank

[Diyplumber427]

My 50 gallon cold water tank in the loft has sprung a seeping leak. It only leaks if completely full so I am currently part filling it!

It’s got 3 outlets - hot water tank, shower pump and a possibly unused one to a pre shower pump fitted gravity shower feed.

Can a reasonably competent DIYer replace it?

I’ve got an estimate that says it’s a whole day job for two plumbers at almost £2k!

 

[oldbuffer]

1. Not a terribly difficult job.
2. However:
2.1 Needs a base to sit on. 18mm marine ply a little larger than the base of the new cistern. NOT MDF
2.2 Getting the new one in (and the old one out) can be difficult to impossible depending on loft hatch size.

 

[Diyplumber427]

Hi meant to say. It’s already on a ply platform and the lift hatch is at least 60cm by 60cm

 

[HERTS P&D]

This one is 610mm x 500mm, so check your measurements again, also you will need good height to push it up into the loft.

https://www.screwfix.com/p/polytank-cold-water-tank-50gallon-uk-1190mm-x-610mm-x-500mm/10134

Also get more quotes.

Andy

 

[HERTS P&D]

Post some pictures of your cold water tank.

Andy

 

[Diyplumber427]

It’s 59cm x 59cm x 112cm long

 

[Diyplumber427]

Here’s the outlets

 

[Scally-Ho]

Is the plastic tank body itself actually leaking, or is it filling right up to the ball valve and leaking at the point the ball valve tail passes through the tank wall? The times I've seen that happen are far too many to recall. If the overflow was fitted correctly that should clear too much water; it should be lower than the ball valve, but all too often I've seen that incorrectly fitted too.

 

[Diyplumber427]

Hi. Good suggestion but it’s not over filling. It seeps when it’s full and not when 2/3rds full!

I’ve checked all the lower outlets and they are all dry.

 

[Scally-Ho]

Hi. Good suggestion but it’s not over filling. It seeps when it’s full and not when 2/3rds full!

I’ve checked all the lower outlets and they are all dry.

Then yes, sadly it does read as though that tank does need replacing.

 

[ChrisJP]

Have you located where the tank is actually leaking from? If none of the pipe connections are leaking, and it's not leaking around the fill valve connection, then there must be some sort of pinhole that's formed. But that's pretty much unheard of with a plastic tank.
You only need to go to all the hassle of replacing the tank if the body of the tank somehow has got a hole in it. If any of the connections to the tank are leaking then you just need to remake these with suitable sealing washers

 

[Scally-Ho]

Is it actually a confirmed leak to the tank body? It's not insulated and it could be heavy continuous condensation.

 

[Diyplumber427]

Hi it was insulated but it got saturated so I took it off. When full the water appears from underneath the tank. All outlets have no leaks.

 

[Nige F]

Have you got woodworm - seriously - a M8's tank had them underneath . leaked . empty it and have a look

 

[Hugh Jaleak]

Have never known a plastic cistern to start leaking unless without cause. Ferham were/are one of the larger, reputable manufacturers, provided the cistern was installed as per requirements, and hasn't been subjected to any external forces, its unusual for them to just start to leak.