dual tanks - dual ball valves????

[alfacapone]

we have dual small storage tanks in the attic connected together with 22mm pipe. One feeds the low pressure cold and hot water. Question is that both tanks have a supply and ballcock taken from the common 15mm rising main. Because the ballcock valve in each tank operates slightly differently, when the level drops one valve will operate to make up the loss leaving the other a "dead leg" - consequently freezing up (and causng flooding once already) . Today I removed one side of the dual supply to one of the tanks ie the one with the longer supply pipework that has now frozen twice in the past 2 weeks.

Question - Did I really need a supply to each tank? With large bore pipework to bath: 22mm, and only a single 15mm supply now to both tanks do I run a high risk of "starving" the hot water cylinder??

Any comments appreciated.

 

[spraggo]

we have dual small storage tanks in the attic connected together with 22mm pipe. One feeds the low pressure cold and hot water. Question is that both tanks have a supply and ballcock taken from the common 15mm rising main.

It depends on how good the incoming mains water pressure is and what the actual size of the storage tanks are. Is it not possible to adjust the ball valve that keeps freezing so that it is the first to open. I would have thought the priorty here would be to get some good pipe lagging.

 

[Burnerman]

Usually 1 fill valve is best, if only to prevent the issues that you mention - as one will 'fight' the other.
The tanks are usually connected with a 22mm pipe so thats ok. It depends if you 'run out' of hot water really - the copper cylinder won't come to any harm, only the flow will reduce until the header tanks replenish themselves.
Either way - pipe lagging is essential to stop them freezing, together with insulation piled on the tank lids.
John

 

[alfacapone]

thanks both for the comments. First freeze happened with old poor lagging so had relagged with new after fixing leak.

Lagging is obviously recommended but many forget it only delays the feeze if the fluid inside the pipe is not being replenished as a result of flow. If the fluid is static eventually the contents will reach ambient temperature which in these temps can be quite quick. Temp in attic this morning was v low, water dropped on to walkboard was freezing in a fairly short time.

I thought of altering the "balance" betweenn the ballcock operation but then thought the other piperun might be at risk.