Leaving capped old mains water pipe branches underground.

[epsilonGreedy]

A couple of weeks ago I discussed how I intended to supply mains power to the static caravan with a view to simplifying the eventual rerouting of power to the long term consumer unit in a weather tight house. Now I face a similar conundrum with supplying water to the caravan that will not result in a compromised long term mains water supply to the house.

 

My concern relates to leaving two capped and pressurized redundant branches underground in the mains water supply pipe before it enters the house footings.

 

I am considering two plans for the following supply route.

 

1.0m from road to water meter sunk into the verge on the plot boundary.

1.5m from meter to the builder's supply stand pipe inside my plot.

3.0m trench 750mm deep from standpipe to house footings blockwork and thru wall entry hole to house floor void.

16.0m around still open footings trench at 600mm deep plus 4.0m shallow'ish trench to underbelly of the static caravan.

 

Option-1 (least pipe used)

1. Fit T connector at standpipe base 600mm below ground and run main supply pipe 3m to the house footings in 750mm deep trench.
2. At house footings add another T connector to branch off 20m of pipe to supply static caravan around external footings trench.
3. Plus from the same T connection run the other branch through footings wall to future suspended floor void and leave large coil capped.
4. One year from now when the builders supply pipe and caravan are retired, cap the caravan supply branch near caravan and leave buried at 300mm deep with some insulation and then dig down to base of standpipe and cap the pipe end.

 

Option-2 (more pipe/simpler long term mains supply to house)

1. Lay long term main house supply pipe in trench between house footings and stand pipe with a second spare coil left above ground near the standpipe but leave unconnected.
2. Add T connector at standpipe base 600mm below and run 24m of pipe to the caravan and as a result have two pipes buried for 3m between standpipe and house footings.
3. In one year extend trench from standpipe to water meter, connect the long term supply pipe coil to the water meter which results in a jointless and branch-less supply direct to the house.
4. There will be no need to cap the redundant branches to the caravan and standpipe because the whole 27m run of pipe will be disconnected and left buried.

 

Option-2 feels like a proper solution.

 

[Mr Punter]

Can't quite picture this but it is not advisable to leave a long capped off dead leg as water can stagnate in the pipe.  Also, if you do a below ground connection, try to locate it so that if required in future it can be exposed and replaced.

[epsilonGreedy]

20 minutes ago, Mr Punter said:

Can't quite picture this but it is not advisable to leave a long capped off dead leg as water can stagnate in the pipe.

 

 

Water stagnation was one of my concerns, there is probably some regulatory stuff on this matter because of the danger of the stagnant water getting drawn back into the mains supply. They are concerned about this subject in marinas these days where a myriad of branches supply the floating pontoon standpipes.

 

The other concerns are that having two T connectors inline to the final house supply might impede flow rate plus capping the redundant caravan supply at a full 750mm deep would involve more digging.

 

The dead leg to the removed standpipe would be short, say 200mm.

Edited October 9, 2018 by epsilonGreedy

[Jeremy Harris]

I'd not worry about a short dead leg, as the incoming supply will have some residual disinfection capability (as long as it remains sealed) and there are often longer dead legs within a system anyway, like runs to outside taps that may stay unused for months.  I'd be inclined to find a way to disconnect things like your disused temporary supply, though, if you can.

 

To put the stagnation issue into perspective, though, it's worth also thinking about all the dead legs in the incoming supply, from things like communication pipes fed from the main (usually without a NRV or stop cock) to houses where occupants might be away, or where the house is empty, or even all the communication pipes that will be laid and may sit for months without being used on a new development.  One of the reasons the water supply companies still use chlorine treatment is because of the residual disinfection effect it provides to deal with areas where water may sit in pipes for a long time. 

 

Some countries are switching to using ozone disinfection (which is what we have on our private supply) because it doesn't leave chlorine, and perhaps more importantly, the breakdown products of chlorine, in the water.  This goes down well with consumers, as the water tastes and smells better, but has the disadvantage that there is no residual disinfection from ozone; it breaks down far too quickly to have any effect beyond an hour or two of being injected into the supply.  Provided that the system doesn't develop problems such that contamination can get into the water, then the lack of residual disinfection isn't a problem,  but our water infrastructure still has lots of pretty old pipes and tends to suffer from a lot of leaks as a result, with the potential that contamination could enter the system.

[PeterW]

Can you not turn the standpipe into a permanent garden tap ..?? Standard 25mm MDPE doesn’t tend to stagnate that much - you can blow it through fairly easily when you connect the main house. 

 

A pair of tees won’t restrict the flow either as long as the branches come off the main run. 

 

Other option is to put put your own bundy box after the static pipe and then isolate there with an underground stop valve - just turn it on when you connect the house. 

[Bitpipe]

12 minutes ago, PeterW said:

Can you not turn the standpipe into a permanent garden tap ..?? Standard 25mm MDPE doesn’t tend to stagnate that much - you can blow it through fairly easily when you connect the main house. 

 

A pair of tees won’t restrict the flow either as long as the branches come off the main run. 

 

Exactly what we did - the final configuration is 32mm mpde from our side of the stopcock to house with a T just after the meter to 20mm mpde for a pair of garden taps - one of these was the original feed for the caravan (which sat at the rear of the house).

 

Blue MPDE is cheap so I wouldn't worry about economising too much there and over complicating your design.

 

[epsilonGreedy]

11 minutes ago, PeterW said:

Can you not turn the standpipe into a permanent garden tap ..??

 

 

Its a thought, this front corner of the house is furthest away from the garage/utility area where I expect to fit the principal outside gardener's tap plus no concerns about regular splashing from a wall mounted outside tap making bricks damp.

 

15 minutes ago, PeterW said:

A pair of tees won’t restrict the flow either as long as the branches come off the main run. 

 

 

I was looking at a catalogue of water pipe parts and noticed that white plastic collars were shown next to the T connectors, so I assumed these were fitted internally at each joint and hence my concern about reduced flow. The water pressure is however phenomenal, so much so a garden multi pattern jet attachment is painful directed at my hand. 

[ToughButterCup]

26 minutes ago, Bitpipe said:

Exactly what we did -[...]

 

Exactly what we plan to do.

[Temp]

Instead of using underground T connectors I'd bring the blue HDPE mains feed up through into the house using 110mm drain pipe as a conduit. Right next door, perhaps in the same 110mm pipe install another length of HDPE going back down and out again to the static caravan. Connect the two temporarily say 12-18" above FFL. Wrap loads of insulation around it.

 

Later fit suitable valves so you can turn off water to the house or just to the static van. If you replace the static van with a shed it can be handy to have a water supply out there.

 

[epsilonGreedy]

7 hours ago, Temp said:

Instead of using underground T connectors I'd bring the blue HDPE mains feed up through into the house using 110mm drain pipe as a conduit. Right next door, perhaps in the same 110mm pipe install another length of HDPE going back down and out again to the static caravan. Connect the two temporarily say 12-18" above FFL. Wrap loads of insulation around it.

 

Later fit suitable valves so you can turn off water to the house or just to the static van...

 

 

This option went through my head last week as I was digging the 3m trench but I dismissed it out of concern over creating extra holes in my footings and/or rodent entry points. The advantage with your extra valves idea is that I would not have to schedule a point in time switch from caravan to house.

[joe90]

We also are having an outside tap where the caravan was during our build, we are also having an outside waterproof socket using the electric cable that fed the van.