Moving and replacing cold water storage tank

[Warrior]

I need to move my cold water and central heating storage tanks. They are both plastic but need replacing due to their general condition, corroded plates, twisted sides etc probably due to poor installation by a previous owner. The cold water tank is 120 gallon ish and the CH tank is 5 gallons ish.

Firstly, I have two bathrooms (1 with bath, both with a pump fed shower) and a total of 3 toilets. The tanks are in the roof which gives about 4 feet for a head of water from bottom of the tank to shower heads. The pipes are all 22mm.
Can I reduce the size of the cold water tank a bit as it takes up so much space?

Secondly, is it better to use copper pipe or to try out the plastic pipes I've seen recently?

and finally, does anyone make a "combined" double tank, as in they are two tanks but moulded together?

I'd appreciate any help.

Thanks

Ian

 

[nysk2008]

Your Cold Water Storage and F&E tanks need to be kept seperate, plastic pipe in the loft would be fine as you dont really see it but my preference would be to run it in copper. As you have 2 bathrooms and 3 toilets I would change the cold water storage like for like but others on here may have other options - depends really on your mains pressure and how quickly it would refill the CWST

 

[Gray0689]

You could change for a coffin tank would give you more room and 120 gallon is a big tank normal is 50 gallon but could of been over sized if your incoming mains is really poor

 

[stevetheplumber]

with two power showers you may have problems if you reduce the tank sizes id run both showers full bore for 10 minutes and see if your existing tank levels are dropping signifigantly

 

[WaterTight]

and finally, does anyone make a "combined" double tank, as in they are two tanks but moulded together?

You can place your f+e above your CWSC and in close proximity. Just need to built something for it to sit on and have room to access CWSC and be able to lift it's lid.

 

[steadyon]

Couple of things to think about:

1. A fifty gallon (220 / 240 litre) tank full of cold water weighs almost 1/4 tonne. Wherever you move it to must provide adequate support for this weight. Ideally over a load bearing wall. Must be on a solid wooden base, 18mm or 25mm ply (waterproof) NOT MDF.

2. If you make your F&E tank higher than your cold water storage cistern, then in the (unlikely) event of the coil in your hot water cylinder developing a leak, you will get central heating water (dirty, with inhibitor chemicals) in the hot water supply. If the F&E tank is lower than the cold tank, the same leak cause the F&E to overflow, warning you of the problem.

 

[Warrior]

Thanks to you all for your help. I have checked the outflow with the two showers running, two sinks and flushing all 3 toilets, the water only drop about 6 inches and filled very quickly as soon as the toilets filled. The rising main is pretty powerful and the water softener has a pressure reducer? fitted to it set at 3 or 4 bar.

The plan is to put the new tank atop a supporting wall so the weight bearing shouldn't be a problem.

Hope to get on with it tomorrow.

Thanks again

Ian

 

[WHPES]

Tank must be fully supported along its base by heavy timbers (not chipboard or MDF) and extend 150mm around either sides to take into account any slumping caused by overheating of the boiler. F&E should be at a lower level than the CWSC. Cold outlets for showers must be lower or in the bottom of the tank, than the hot oultet (so hot water runs out first). Make sure you install inlets, outlets, overflows etc and byelaw kit in accordance with the regulations (usually detailed in the brochure which comes with the tank. The tank must have a closely fitting lid (for hygiene) and be installed according to regulations. This is especially important for showers (see legionella topic).