Hot water tap stops when turning the cold tap on.

I have a strange problem. We have an old house and the plumbing is old and the pressure is low, but my biggest problem is this.

If i turn on the hot water to fill the bath it runs fine. As soon as i turn on the cold water the hot water stops running. As soon as i turn off the cold water, the hot splutters for a while and eventually starts running again.

I have a 400KPA geyser, and have just fitted a 400KPA pressure valve to see if that would help, but it hasn't.

It seems to me that the cold water coming into the house stops supplying the geyser when i turn on the cold tap, and therefore hot water stops flowing.

How can this be sorted out?

Thanks in advance.

sounds to me like you have old galvanized pipes that are clogged up with calcium and rust.

if this is the case, you need to repipe the system.

sorry,,,not what you wanted to hear

others may have a different opinion

yes, i believe we do have galvanised pipes. Thanks for the information, that sounds like a big job!!

What maybe occurring is the hot line has restricted flow. When you turn on the cold the water, flow is going to take the path with the least resistants' through the cold supply.
make sure you water supply valves are open all the way.

If you have hot only on how's the Volume if you open a cold faucet else where. does it do that only at the tub or at other fixtures as well


Had a job the other day, customer's landscaper told him he needed to connect his irrigation sprinklers to his water service before his pressure reducing valve. there wasn't enough pressure to lift his pop-up sprinkler heads.

Turned out the main water shut off valve at the curb in a ground box was only partially opened.

Not really sure what a geyser was so I looked it up, Sort of.
Still not really sure. Are these electric water heaters used in gravity fed systems?

Not Sometime we use here

I stumbled on to a site with some tips on things to check.

This is from a company in South Africa.

http://www.holleysplumbing.co.za/index.php?option=com_content&view=article&id=126&Itemid=116