Confused

[Hugh Rynal]

With the hosepipe ban over I decided to save a few quid and wash the car at home yesterday. I ran the hose from the mixer tap in the utility room with hot and cold on full. A while after using the hose, water started trickling from the coldwater tank overflow pipe sticking out under the eaves which fairly quickly became a torrent of water. As I had already stopped the hose and the water was still coming out, I turned it off at the mains until it stopped. I then remembered this happened last year when I used the same taps on full power. But why doesn't the same thing happen when I run a bath with both taps on which is a far greater quantity of water per minute. What is causing this ?

 

[kevplumb]

the cold (mains pressure ) if feeding back through the hot (tank fed)

bath mixer has two channels to stop this

 

[Hugh Rynal]

Not sure I understand what you mean. I initially thought that it may be that the demand on the tank meant that the tank was filling up quicker than it was emptying due to water pressure and pipe sizes but I think the utility room sink is fed direct off the mains so the demand on the tank would be less than both bath taps.

 

[kevplumb]

ok if the tank was filling up quicker the ballvalve would stop it overflowing

you are pushing mains water back up the pipe

all it needs is a check valve on the hot

 

[namsag]

Or stop being a southern softy an just use cold water to wash the car. God it was nearly double figures yesterday almost a summers day. Soon be T shirt weather,

 

[Hugh Rynal]

namsag


Think I am with you know kevplumb. I assume that when I am not using the trigger on the hose the pressure on the open cold tap is forcing mains water up into the hw tank which in turn refills the loft tank. Correct ?

Where would the check valve need to go. Some where between the hw tank and loft tank ?

 

[BoxBasher]

Right under the sink/hot tap would be the best place. You should be able to get at the pipework quite easily there, even better if yo uahve flexi-connectors because you can just stick the check valve between threaded fitings...