Why do some hot water taps do this?

**Bluedog** · 29-06-10, 03:34 PM

yes , that was an interesting program. they do go bang badly.

on a similar note, this morningit was -8 C here and everything had frozen. no taps ran.
on mornings like this turning on the hot tap will allow water to run from the hot-tank but because the pipe from the 2000litre header tank is frozen and the shepards crook is also frozen, the hot-tank crumples like a empty coke can!
those water tanks are designed to stay round when there is water inside , but create a vaccuum and they just implode being just a copper jacket with insulation around the outside. after this happened a few times and i had to get in the roof and braze it up a lot we got someone to make up a stainless steel tank and that solved the problem.
its still heated from the thermosyphon off the woodstove in the kitchen though.
no electric boost
cheers

**gordon_s1942** · 30-06-10, 02:36 PM

Bluedog,When my stepfather's donkey burst after a couple of heavy frosts in Lithgow, I got him to light it late in the afternoon as he had always lit it in the mornings.
His was the external boiler and 60 gallon tank set up on a framework.
When we knew there was a frost setting, he tried to do the fire as late as possible and we had no further problems after that.
The only other solution other than replacing the tank as you did would be to try to use a pump to circulate the water around the system which I think would be a nuisance to set up.
These last 3 days have seen Temps down to Minus 3 C to Minus 10 C depending your location along the Tablelands.
I didnt know squat when I put mine in years ago and now I have almost no pressure out of the shower head so I put a small pump into the HOT line, not the best idea but it works.

**viper5150** · 01-07-10, 05:16 PM

Originally Posted by Fernbay

Hot water expands. It builds up pressure in the HWS tank. When you open the tap the pressure gradually decreases back to mains water pressure

Close, but also add in the hot water expanding the tap washer and decreasing the flow. Copper stemmed washers are far worse that plastic due to copper being such a good conductor of heat.

The tank pressure will only build so much before the relief valve does its thing and releases the pressure. I would doubt that any pressure build up would have an influence on initial pressure. The incoming cold water that fills the tank would more than offset the pressure reduction with the inlet pipes being 3/4in and the outlet being 1/2in.

On a side topic, you can now get a little gadget that eliminates the cold water in the pipes before you get the hot water coming through. You plumb it in the opposite side of the house to the heater and an electric pump circulates the hot water, rather than having it sit in the pipes and go cold between the heater and the outlet you want to use.

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