Burst Pipes headscratcher

[jonbenj]

Hi there.
I'm new to this forum, so be gentle. Looking for some advice. I've had frozen pipes over the last week, but my system doesn't seem very logical. I've got a main supply coming out of the ground which supplies combi boiler and upstairs cold water. This has a stopcock just above the ground. The initial run goes up the side of the wall for about 70cm before entering house. It was boxed in but otherwise unisulated, and has burst and frozen. I've put in a new piece of plastic pipe temporarily,mandminsulted with 22mm thick foam. Should I replace with copper or will the plastic be ok?

I was surprised when this pipe froze that I was still getting cold water out of my kitchen tap. The kitchen was extended before I moved here. I was unable to find a seperate stopcock anywhere for this supply. All was fine until Friday night when this froze as well. It thawed slightly yesterday and unfortuneately this pipe had burst as well. No hatch in floor meant some emergency demolition was in order. I was able to cut the pipe on the supply side of the burst and put in a check valve to stop the cold water flow. What's really puzzling me is that if I turn on the hot tap in the kitchen whilst I get hot water out of the tap OK I ALSO get hot water flowing back out of the burst side of the COLD supply pipe.

I should add for clarity that the heating circuits are undamaged and functioning OK, and that the upstairs hot and cold supplies are intact and have no effect with whats happening with the kitchen.

any advice is most welcome, even though I think I'll be claiming on the insurance for it .


Thanks in advance

jonbenj.

 

[Burnerman]

Is your kitchen fed by a cold water storage tank in the loft?
John

 

[jonbenj]

Is your kitchen fed by a cold water storage tank in the loft?
John

Definitely not. Wouldn't be surprised if there's a stopcock buried under the patio somewhere.

 

[Burnerman]

If you were still getting cold water although the supply pipe was frozen, then that part of the building must be fed from another supply somewhere?
You haven't got a mixer tap in the kitchen thats allowing back flow, have you, allowing hot water to come out of the cold pipe? A bit flummoxing, this one!
John

 

[griggs]

turn off stopcock in street, if you still have water on the kitchen cold supply then it must be fed from loft tank as Burnerman has said

 

[dextrous]

or your neighbour

 

[jonbenj]

turn off stopcock in street, if you still have water on the kitchen cold supply then it must be fed from loft tank as Burnerman has said

Like I said, no tank in loft.

Hadn't thought about hot water backflowing through mixer tap. Could that happen?

 

[dextrous]

The original pipe that burst outside- what size is it and where does it go to?

My guess is that, for whatever reason, your supply pipe it teed somewhere between the pavement and your house, one tee goes into the house where it has burst and you've replaced with plastic, and the other goes to the kitchen.

As for you're getting hot water through the piece that you've cut in the kitchen, if you have a mixer tap then no surprises there then, since it is quite possible for backflow to occur from hot to cold or vice versa- there are numerous queries relating to this phenomena on here when people have gravity hot but mains cold supplies.

 

[jonbenj]

or your neighbour

Don't think it's the neighbour's as the supply's coming from MY side of the house. Next doors empty at the moment,mjust been sold.

 

[jonbenj]

The original pipe that burst outside- what size is it and where does it go to?

22mm leads through wall to combi boiler.

My guess is that, for whatever reason, your supply pipe it teed somewhere between the pavement and your house, one tee goes into the house where it has burst and you've replaced with plastic, and the other goes to the kitchen.

Think you're probably right.

As for you're getting hot water through the piece that you've cut in the kitchen, if you have a mixer tap then no surprises there then, since it is quite possible for backflow to occur from hot to cold or vice versa- there are numerous queries relating to this phenomena on here when people have gravity hot but mains cold supplies.

Didn't know this could happen. I thought on modern mixers the hot and cold flows were seperated right up to the end of the tap spout. How can water backflow if this is the case?

 

[dextrous]

So, ideally, it should have been teed inside the building for the boiler, but if the floors are solid, then it seems pretty obvious what the easier option at the time was.

Not all modern taps work as you describe - as you are in the process of discovering One way of resolving this issue is to install double check valves to prevent contamination of the mains "wholesome" water supply.

 

[jonbenj]

So, ideally, it should have been teed inside the building for the boiler, but if the floors are solid, then it seems pretty obvious what the easier option at the time was.

Aye right enough. The floor at the back of the house where the kitchen used to be is solid, so I guess the builders took the path of least resistance. There obviously wasn't enough profit in the job to stick some insulation on

So do you think my external plastic pipe repair will be ok or should I swop it back to copper?

 

[dextrous]

If it's working as well as before, no reason to change it

 

[jonbenj]

So farit's working better than before,cos it hasn't burst yet, tho the temperature today did rise to an almost equatorial 4.5 degrees

Is the plastic pipe more or less frost resistant than copper?

One other probably dumb question: what's the difference between a double and a single check valve? If as i suspect the double has 2 non return valves, is 1 not good enough, or is it a belt and braces job?

Sorry for all the questions Dextrous. Have some thanks.

 

[dextrous]

Some say that plastic is a bit more self-insulating and indeed a bit more elastic than copper. Think you need to take care that it doesn't overheat now you're into tee-shirt weather.

Your description of single v double check valve is correct. I may be incorrect here (watch the others gather like flies round the proverbial bandwagon ), but double check should be used to protect the mains "wholesome" (it used to be called "potable") supply from contamination.