Hi
I have a gravity fed low pressure hot water cylinder. I have attached a new supply tank to the house further up the hill. It has a 1.1/4 inch pipe running from it, our pressure is much better all over now, but we have the problem of water coming out the top of the hotwater over flow pipe, due know doubt to the height of the supply tank, can I extend the over flow to match supply tank height and if so what is the best way of doing this.

That is exactly what you must do. Depending how hot the over flow pipe gets, you may need to select a hot water resistant pipe. How high will it need to be? I am assuming little water flow in the pipe, just a stand pipe to allow pressure to equalize with the water running out. CPVC would be the cheapest, but I am not sure how high you can run it without support. What ever you select, you need to make a water tight joint and run the pipe up high enough. A compression fitting should be good enough if the old pipe isn't threaded on top.

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Originally Posted by labman

That is exactly what you must do. Depending how hot the over flow pipe gets, you may need to select a hot water resistant pipe. How high will it need to be? I am assuming little water flow in the pipe, just a stand pipe to allow pressure to equalize with the water running out. CPVC would be the cheapest, but I am not sure how high you can run it without support. What ever you select, you need to make a water tight joint and run the pipe up high enough. A compression fitting should be good enough if the old pipe isn't threaded on top.

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Labmans advice. Now as to how high the standpipe should be?? To ascertain this you're going to have to calculate the differential in heigth from the top of the newly installed supply tank and the top of the low pressure hot water tank and make the stand pipe 8 to 12" over that figure.
there are several ways you can do this. The most reliable would be to use a "line of sight" or a Lazar transit and shoot from the supply tank. Another would be to use a thin wire running from the top of the supply tank. Stretch the wire as tight as you can. Install a line level about half way between the two tanks and when the bubble reads level measure down to the low pressure hot water tank. Or you can work it,"hit or miss".; Just pop up a stand pipe and if water still overflows add another piece of pipe until it stops. As Labman advised, convert to CPVC for the standpipe. Good luck, Tom

Thanks for the advice,
As my tank is a bit beyond hooking a string line up, I will try line of sight.
So you reckon a compression fitting over cvpc will do it?
Excuse my ignorance a stand pipe? Is that a pipe welded to a stand and are they available from plumbing stores? Can you just slide them over copper pipe and clamp. I have a feeling this is going to be 2/3m heigh maybe a little more.
Thanks again
Ged

Stand pipe. It is any old pipe allowing water to stand and equalize pressure. If your old pipe is copper, you should be able to buy a CPVC union that will fit it and a length of CPVC. Slide the union over the ends of both pipes and tighten them up, and you are done. For all the longer piece you need to add, copper won't cost much more, and if you can solder pipe, just buy a copper union.

I will do that
Thank you
Ged