Using Balanced cold

[Mgrant]

Hey, do people tend to use the balanced cold connection on unvented hot water systems. To feed all the cold supplys on a house,bar the kitchen sink tap which is taken straight of the mains. Or is balanced cold not often used? I often see it just capped off on the composition valve in the cylinder cupboard.

 

[Killy Bing]

..........well...

 

[Ch4 plumbing]

If you think hard enough the answer will come to you.....

 

[Ermintrude]

If you do training course you will know the answer !

 

[Best]

Totally new build or complete replacement of plumbing system & you would obviously do the job properly - even if it was not strictly a requirement of regs.
Mixer taps & showers are better with balanced supplies.

 

[kirkgas]

It depends on the layout of the house and the fittments, but if going unvented I think the benefit of getting rid of the storage tank and changing everything to a balanced supply is the better option

 

[Best]

Possibly the OP is looking at some unvented cylinders that have replaced on old gravity systems & the mains pipe has not been replaced to go straight to the uv unit. Then it is too big a job to lift floors etc & maybe impossible due to solid or tiled or hardwood floors.
If it is a totally new plumbing system, then the plumber is an idiot to not have piped balanced cold & hot to every tap or shower using the PRV connection for the cold supply.

 

[Mgrant]

I no its so the hot and cold pressure is balanced for mixer taps to work correctly, is the kitchen sink tap usually piped off mains cold though still? The hot water will be 3.5 bar and if balanced cold wasn't used and the mains was 4 bar would it really make much of a difference?

 

[Best]

I no its so the hot and cold pressure is balanced for mixer taps to work correctly, is the kitchen sink tap usually piped off mains cold though still? The hot water will be 3.5 bar and if balanced cold wasn't used and the mains was 4 bar would it really make much of a difference?

Think about it, - If the kitchen sink mains just comes off the stopcock & is 4bar, who's to say that the pressure won't increase at times of lower demand or that the water supplier will not increase the pressure for some reason?
If the tap on the kitchen is a mixer, (nearly all are) then the mains can push through the hot pipe & into the unvented unit. This can also happen if body of mixer has a pin hole in casting & can do that when tap is off.

 

[Roger Welton]

Which is why all mixers are installed with check valves as per the water regs.

 

[Best]

If an unvented MIs state that the max incoming pressure regulated by supplied PRV is, say 3bar, then it has to be 3bar, not any higher.
Check valves fitted on the sink mixer will be good practice but where there is a cold supply unregulated by the cylinder PRV, the unvented cylinder manufacturer probably will require a double check valve to be fitted on hot pipe leaving cylinder.

 

[Mgrant]

Think about it, - If the kitchen sink mains just comes off the stopcock & is 4bar, who's to say that the pressure won't increase at times of lower demand or that the water supplier will not increase the pressure for some reason?
If the tap on the kitchen is a mixer, (nearly all are) then the mains can push through the hot pipe & into the unvented unit. This can also happen if body of mixer has a pin hole in casting & can do that when tap is off.

So You'd feed every tap including the kitchen sink off balanced cold. Have seen the balanced cold just caped of on many new build sites. What about on a vented system were all the cold supply's are feed of mains but the hot which is obviously a lot lower pressure with it just being tank fed. Wouldn't that give huge issues with mixer taps?

 

[mutley racers]

Non return valves are needed otherwise you will have water coming out of the overflow from the cold water storage tank in loft

 

[Best]

So You'd feed every tap including the kitchen sink off balanced cold. Have seen the balanced cold just caped of on many new build sites. What about on a vented system were all the cold supply's are feed of mains but the hot which is obviously a lot lower pressure with it just being tank fed. Wouldn't that give huge issues with mixer taps?

Ideally, in a all new job, the mains will go straight to where the unvented cylinder is & to a stopcock, cylinder PRV & all cold supplies are from this PRV.
On your question of gravity vented hot & mains cold in houses, - yes, - it can & will cause issues as the mains can push back into hot pipes at mixers & if you have a faulty pin holed mixer, the mains will go to vented copper cylinder & up the cylinder cold feed into cwt & keep overflowing it.

 

[chris watkins]

Question - Before unvented systems were allowed English plumbing systems had mains cold water (high pressure) on one side of a kitchen mixer tap & gravity fed hot water (low pressure) on the other how comes there was no back feed to the hot ? and both hot & cold could be on at the same time ??

P.S. Unvented cylinder manufacturers have no requirements to to install back flow protection devices on there outlet but there most certainly is a requirement to install single checks to both hot & cold where water mixes under the Water Regs, this is a requirement not a recommendation.

P.P.S No checks required on the mixer tap in the question above, why ?

 

[Best]

Telford require a double check valve on the hot outlet on jobs where one or more cold outlets are not balanced.

 

[Best]

Old mixers connected with gravity hot & mains cold had to have back feed to some extent if mains pressure was decent & no check valves fitted. Just nobody notices.
Old mixers mostly mix in the body before going into single piped spout.

 

[chris watkins]

Old mixers connected with gravity hot & mains cold had to have back feed to some extent if mains pressure was decent & no check valves fitted. Just nobody notices.
Old mixers mostly mix in the body before going into single piped spout.

Perhaps you have different taps over there but we have divide flow & have had for a very long time, so hot & cold are kept separate. They only mix when they leave the spout, so no back flow & no requirement for check valves.
It is only the cheap imported taps which mix in the body & cause all these problems.

James1 - I would strongly recommend that all the cold's to mixer taps & showers (not the kitchen sink, see above) are taken from the balanced port or if that is not possible on an existing system then install a dedicated pressure reducing valve on the cold.
We have so many problems with back feeding from the higher pressure cold to hot. Even if check valves are installed they break.

 

[Best]

Perhaps you have different taps over there but we have divide flow & have had for a very long time, so hot & cold are kept separate. They only mix when they leave the spout, so no back flow & no requirement for check valves.
It is only the cheap imported taps which mix in the body & cause all these problems.

Lol! No we are in the 21st century here & are same as rest of UK - modern mixers are all separate flows here, but there are thousands of mixers that are not dual flow still around & some I know for a fact were being sold within the last 20 years.
One thing I would say about a plumber not using a balanced mains supply to the kitchen sink is - what if that mixer or a later mixer is faulty & water passes through the body? Still better ideally that it is balanced cold for that reason.

 

[Mgrant]

If balanced cold wasn't used and problems occurred could a pressure reducer be put on the cold mains and set to 3.5 bar so its the same as the hot pressure.

 

[Ermintrude]

Not really going to work, cold may fluctuate and 3.5 is max it could be right down at 1.5. Might have to be a suck it and see, start at 1.5 and work upwards on prv

 

[sheff paul]

Hey, do people tend to use the balanced cold connection on unvented hot water systems. To feed all the cold supplys on a house,bar the kitchen sink tap which is taken straight of the mains. Or is balanced cold not often used? I often see it just capped off on the composition valve in the cylinder cupboard.

Normally 1st fix so the kitchen tap and outside tap are on mains,take a 22mm straight to the cylinder cupboard,or have a separate prv under the sink.James 1 this is a good intelligent question,shows you are thinking

 

[chris watkins]

Not really going to work, cold may fluctuate and 3.5 is max it could be right down at 1.5. Might have to be a suck it and see, start at 1.5 and work upwards on prv

Surely even if cold mains is less than the PRV serving the hot it will still be the same ??
The hot is often at a greater pressure than the cold system due to expansion when it is heated.

 

[chris watkins]

If balanced cold wasn't used and problems occurred could a pressure reducer be put on the cold mains and set to 3.5 bar so its the same as the hot pressure.

Yes, that should work.

 

[Ermintrude]

What I was trying to say was it might be difficult to set up. Start off with prv set at 1.5 on cold 3 on hot and see what it's like, if ok climb up to 2 and 3 and 3.5 over a few weeks?

 

[sheff paul]

Surely even if cold mains is less than the PRV serving the hot it will still be the same ??
The hot is often at a greater pressure than the cold system due to expansion when it is heated.

noticed when I was commissioning last week the hot does come out a bit quicker than cold

 

[voivod]

When was on sites (5 years+ ago) . We had drawings from the cylinder / heating manufacturers.
They used to ask us to fit a prv at sink 3bar ...then you had the prv which came with the cylinder aswell .
Some asked for full pressure to cyl prv and a seperate prv for colds
And some wanted the cylinder prv under the sink with a seperate balanced draw off for cold and another pipe from the prv to the cylinder.
All combis got a prv on incoming mains too.
In edinburgh have seen mains at 6/7 bar so think is a good idea
( which is also handy when we were pressure testing the systems up to 10 bar.,, loads less pumping )

 

[kay-jay]

good practice to use a balanced cold supply, even if there are no mixer showers or taps as there may well be in the future. if its not a new build and there would be a lot of upheaval lifting floors and whatnot then i would whack an additional prv under sink.

 

[Mgrant]

So are you saying if possible on a new build to have the cold mains enter were the cylinder is located in the house and have the houses stop tap there. As apposed to the usual place of under the kitchen sink. Feed the cylinder off this, then take all the cold supply's to the house from the balanced cold connector on the cylinders composition valve.

 

[kay-jay]

So are you saying if possible on a new build to have the cold mains enter were the cylinder is located in the house and have the houses stop tap there. As apposed to the usual place of under the kitchen sink. Feed the cylinder off this, then take all the cold supply's to the house from the balanced cold connector on the cylinders composition valve.

No. Stoptap on entry as per regs. Then pipe to cyl cupboard and take a balanced cold to oitlets

 

[Mgrant]

Ideally, in a all new job, the mains will go straight to where the unvented cylinder is & to a stopcock, cylinder PRV & all cold supplies are from this PRV.
On your question of gravity vented hot & mains cold in houses, - yes, - it can & will cause issues as the mains can push back into hot pipes at mixers & if you have a faulty pin holed mixer, the mains will go to vented copper cylinder & up the cylinder cold feed into cwt & keep overflowing it.

So even toilets would be taken off balanced cold? Have seen that a lot of cylinder manufactures prefer you to have a uninterrupted cold feed to the cylinder.

 

[Best]

So even toilets would be taken off balanced cold? Have seen that a lot of cylinder manufactures prefer you to have a uninterrupted cold feed to the cylinder.

Yes, all supplies to bathrooms etc to be balanced.
By uninterrupted cold supply to cylinder the manufacturers will have two reasons for that, - no robbing of the higher pressure mains before it reaches the cylinder & also balanced supplies to everything from the units PRV point so that no higher pressure water can come back to the unit & overpressure it.

 

[Mgrant]

I was speaking to one rep for unvented cylinders who told us to fit a prv after the stop tap in the kitchen set to about 5 bar. Take the cold for the kitchen off this, as it was a long way to come back from the cylinder to feed. Then take the cold to the cylinder to feed the hot through the prv on the cylinder. Then instead of using the balanced cold connection fit a prv to 3 bar on the cold after its tee'd of to the cylinder and take it back to all the cold draw offs as this would give a better flow then using the balanced cold connection. I wonder why he stated we should fit a 2 prv though. It is a high pressure area around 9 bar.

 

[Best]

Problem IMO with fitting other PRVs is that you will have all these PRVs to check if working correctly & service. They are not always reliable. Also the big worry is some of the mixers - like shower valves & mixer taps, if faulty can put the cold through the hot pipe & to the unvented cylinder.
The idea of putting a separate PRV set to 3bar for the house cold pipes is okay if you really have to in a change over from an existing vented system, but not ideal.

 

[Best]

All the unvented cylinder manufacturer requires is that their unit is safe & is also protected from over pressurising.