Hi preasure hot water.

[philipb]

Hi guys,
Had a unusual day today,fitting new bathroom in 4bed detached with santon unvented hi preasure hot water,turned cold mains off to pipe up bath tap and as i opened hot and cold downstairs to empty the pipes,hot water was coming out off the cold tap.plumbed in bath tap with polyplumb plastic to the tap from the copper that had fed the original bath tap.i used plastic as the tap was going at the other end on the new bath.As i turned the water back on both the hot and cold plastic fittings feeding the tap blow off with two open pipes and water everywhere.your comments would be helpfull.
thanks philipb

 

[Gray0689]

I'd personally have to say you didn't have the fittings pushed on properly

 

[philipb]

Hi Gray0689,
All the fittings were new and pushed home firmly as always,why was very hot water coming out off the cold tap?
Also the customer says the hot tap spits a lot of air when used normaly.

 

[Gray0689]

polyplumb fittings are best ones IMHO never saw any blow off only hep ones
As for hot water is was it a mixer tap you turned on maybe not balanced cold and feeding back through from hot is the expansion vessel on hot side of cylinder

 

[Howsie]

I agree. PP are rock solid.

 

[philipb]

Will check expansion vessel today,when the pipes blew off it sounded like a build up off
air escaping,the two fittings in question were pushed together in my hands on a
bench so i 100% know they were all the way home,the two i pushed onto the tap tails
while i was on my back at arms length never moved.going to speak to santon today
about possible causes of hot water getting into cold pipes,its a little out of my field.

 

[BLOD]

If you have a balanced supply of hot & cold to the bath, when the mains is turned off & the bath taps are opened the expansion vessel will push water out of both taps from the system / cylinder for a short while - & is quite possible to get hot through the cold tap.

 

[AWheating]

retest the pushfit fittingswith a test pump they may be faulty? (ring missing?)

 

[philipb]

Thanks for your comments guys,i think i will contact polyplumb about this,i repiped it all today in copper with no problems.
spoke to cylinder maker who said the preasure relief and preasure vessel should be set at 3.5bar,and no way could it
build up enough preasure to blow two pipe fittings apart.one thing i am not sure about is if air in the pipes
is compressed are the push fit fittings liable to blow off?because its air and not water,it does say on the pack
not to be used on compressed air.should i have left the bath tap open to get the air out and stop it building up?

 

[AWheating]

when filling any unvented cylinder its important to leave the furthest hot tap open to vent the cylinder correctly. pushfit fittingd will hold on with only air in the pipework.

 

[philipb]

Thanks AW,the cylinder maker said the system should be serviced and the preasure vessel and relief checked
for correct operation,how is this done?

 

[AWheating]

it can only be done by an engineer with his unvented qualification/ticket so dont touch it if you have not done the ticket.

 

[philipb]

Thanks for that,i have no intention of thouching it,i just wanted to know a little more about whats involved
so i can talk to the right people

 

[AWheating]

to test the expansion relief valve for example would be easy as you just test it works by turning it, but without the knowledge of what its for, how it needs to be fitted, how its discharge pipework needs to run correctly along with the rest of the system its a pointless test.

you should do the course, and then you can charge for the service

 

[philipb]

Hi guys,just an update on this subject,the customer met a friend at the weekend who does a bit of basic plumbing
and he had two polyplumb fittings blow off last week,thats 4 i know off,am sending my two fittings to them for testing.
My two were bought from wickes in wakefield,polyplumd said they had not had any reports as of yesterday.

 

[pobsdad]

They would say that,wouldn't they?There should be a check valve on the system to stop hot water getting back into the cold,usually built into the pressure reducing valve set.If this is faulty,or in the wrong place,a cold tap can empty the cylinder when the water's off.

 

[philipb]

Hi there,I will check that,there is a problem somewhere as yesterday i was fitting the
shower head,i turned cold mains off and opened the hot and cold taps in kitchen to drain the pipes
and got a cupfull out off each tap.last week when i did the same thing hot water came out of the cold tap
and it ran for 5 mins.

 

[AWheating]

They would say that,wouldn't they?There should be a check valve on the system to stop hot water getting back into the cold,usually built into the pressure reducing valve set.If this is faulty,or in the wrong place,a cold tap can empty the cylinder when the water's off.

if the cold is a balanced connection after the prv/combi valve then it wont stop this.