Balancing water tank of 2 different sizes

[darren72]

Hi All,

I have a problem in one of my project which requires urgent advise. In this project, the existing water tank size is 2m(L) x 2.5m(W) x 2m(H).

Due to additional water demand as a result of additional sanitary fittings, there has been a increase of the effective capacity to 8.4 cu m. As there is space constraint within the plant room, the existing water tank could not be upsize. An additional new tank of size 3m(L) x 3m(W) x 1.5m(H) was added to meet the new eff. cap. The water is supply from the tanks via booster pump to the sanitary fittings within the toilets.

Moreover, there is also structural constraint on exsiting slab where the effective water height within each tank cannot exceed 0.75m.

My question is:

1. If i were to connect the 2 tanks together with a balancing pipe, the eff vol of 8.4 cu m will be equally shared between these 2 tanks, ie 4.2 cu m for each tank. However, due to 2 tanks of different sizes, the water level for existing tank will be 0.84m which exceeded the structural constraint of 0.75m. Any suggestion to solve this problem?


2. If each outlet from each tank is connected to a common pipe first before going to the pump, will this affect the operation of the pump? Please note no balancing pipe is provided in this case.

Many thanks.

 

[plumberdarren]

How good is water pressure and flow on the mains ? Is it nessasary for 2 tanks if the mains can keep up? if this is the way it has to be done i would consider keraflo valves (link below) this way you could balance each tank however bear in mind you could only have the water level at the same height as the smallest tank in both tanks if connected by a common pipe.

[DLMURL="http://www.keraflo.co.uk/products/kb_type.aspx"]KB type - Products - Water valves - Keraflo[/DLMURL]

 

[TGor]

How about lifting up the tank by 90mm which would reduce the water level effectively!!

 

[darren72]

Hi Plumberdarren,

Thanks for your prompt reply.

Just to clarify the Kerato valve which u have suggested is for the case 2 where balancing pipe is not use to link up the tank right? And where should this valve be located? Is it at the pipe outlet from each tank for flow balancing purpose?

 

[plumberdarren]

Just been thinking about this one again and dont feel ive told you the best option. it may be better to have the ball valve in 1 tank, have a link/balance pipe from the far end of that tank linking to the 2nd tank then the draw off to the pumps from the second tank and adjust the ball valve accordingly to give an equal water level as required in each, doing it this way gives you the storage you require and sufficient flow through the tanks.

 

[darren72]

Hi plumberdarren,

In that case, i would need to downsize the new additional tank to the same size of the small tank and would not be able to meet the 8.4 cu m eff cap. Any other way, i can still achieve the eff cap with the abovementioned 2 tank configuration?

 

[HoodedClaw]

I might be missing the problem, tank 1 has the ballvalve setting the water level at 75cm (2 x 2.5 x .75 = 3.75), tank 2 could have ballvalve or if it can refill fast enough from one then balancing pipes also at 75cm (3 x 3 x .75 = 6.75) giving a 10.5 cu m and meeting the .75m load

Draw off the 2nd tank to circulate with one valve and off both into one with 2 ballvalves.

Seems to meet everything so I must be missing something?

 

[plumberdarren]

Sounds spot on as I suggested in p5, just remember all water storage should turn over in a 24 hour period as per water regs.

 

[Gray0689]

Hi All

I Maybe incorrect, but I thought Water Regs now suggest not putting any new tanks in series
(eg: tank1 with ballvalve feeding via balance pipe tank2 with outlets) as tank2 can stagnate at top,

The tanks should be put in parallel, with inlets into each tank and outlets from each tank which can be manifolded back together afterwards.

Thanks

Drayton Tanks
Click for Water Tanks

That is correct way to do it Drayton tanks