Replacing lead water pipe

[J_Ashley]

I've had a look on some more specific forums but I always seem to get good advice here, so here goes....

Whilst we’re having other works done to the house, we’re thinking of replacing the original (150+ years) mains supply lead water pipe with a modern MDPE version. The house is a Victorian terrace, with the exterior stop clock just outside on the footpath and the interior stopclock about 15m further away in the kitchen.

In terms of installing the pipe, we seem to have been quoted for two options:

- Lay a pipe from the boundary that enters below the front bay window, and is run across the sub floor-void entering the kitchen below the plinth area and being connected to the existing riser. The pipe will be laid in insulation, as is mandatory for pipe that isn’t buried.

- Installation via moling wherever possible, so that the pipe is buried (I believe to a minimum of 750mm).

One of my considerations is that I want to avoid damage to the kitchen (as this doesn’t need any renovation), and we’re unsure if the moling intensive method might cause damage.

Any advice on the pros/cons of either of these two methods would be appreciated.

Finally, with regards to the pipe, is there any benefit to going with a 32mm over a 25mm?

 

[finneyb]

Can a man get in the floor void to work? If so I don't see how the kitchen is at risk either way if the connection to the riser is below the plinth .

Personally, I wouldn't want moling under the house unless I had to , OK outside the house and then run in the void and insulate.


Brian

 

[Sideways]

Some friends had a burst under the floor and ended up with 18" depth of water in the void below their timber floor. The dog jumped in for a look one night after they lifted the kitchen floorboards and nearly drowned.
Many months and big bucks to dry everything out and make good. Whatever you do, get it done properly.

 

[sunnybob]

Larger pipe everytime. More pressure, more flow. No brainer.
The moling seems best to me. Minimum disruption. A hole the size of the mole isnt going to bring the house down. If the foundations were that bad the house would already be listing.

 

[MikeG.]

I would move the stop cock location, to the point where the main goes under the wall of the house. Then run the internal plumbing around to the existing stop cock (which you would remove) within the heated/ insulated envelope of the building. The pipe from the boundary should be below 750. Frost isn't the only consideration. The idea of moling underneath a building is frightening, and you still need a big deep trench at the location where it comes up out of the ground.

What I am suggesting might involve removing a kitchen unit to do the initial work, but compared with the disruption of any other option it is far and away the best solution, in my view. Further, it leaves you with the plumbing in the safest possible location, including the best possible position for the stop cock.

Use 1" pipe. There is absolutely no benefit whatever in going above that in a domestic situation. You'll have to step down at the stop cock anyway, so what benefit would you gain from just a few feet of bigger pipe under the garden?

 

[Woody2Shoes]

I would move the stop cock location, to the point where the main goes under the wall of the house. Then run the internal plumbing around to the existing stop cock (which you would remove) within the heated/ insulated envelope of the building. The pipe from the boundary should be below 750. Frost isn't the only consideration. The idea of moling underneath a building is frightening, and you still need a big deep trench at the location where it comes up out of the ground.

What I am suggesting might involve removing a kitchen unit to do the initial work, but compared with the disruption of any other option it is far and away the best solution, in my view. Further, it leaves you with the plumbing in the safest possible location, including the best possible position for the stop cock.

Use 1" pipe. There is absolutely no benefit whatever in going above that in a domestic situation. You'll have to step down at the stop cock anyway, so what benefit would you gain from just a few feet of bigger pipe under the garden?

+1 to what Mike says (I've done a similar project in much the same way, and wouldn't choose to do it differently)! Cheers, W2S

 

[J_Ashley]

As is usual, I need to make sure I’ve actually understood all the comments here….

Pipe lain across sub floor void:
- Less invasive, and so doesn’t have concerns associated with moling underneath the house.
- Risk of leaks means potential water damage to sub floor area, as the stop clock is located after this in the kitchen.

Mike G, Is my below interpretation of your methodology correct?

Mike G Solution:
- Mole (excavation is also possible as it’s only a 3-4m front yard) from property boundary to the front exterior wall at minimum depth of 750mm.
- Add new stop clock at front wall of the house.
- Plumb from new stop clock to current kitchen entry point, removing old stop clock in the process.
- My interpretation is that this is similar to the ‘Pipe lain across sub floor void’, but moves the stop clock to before the sub-floor void run thus giving protection in the event of a leak.

One detail that might be useful – whilst the property is Victorian, the stop clock on the pathway is modern and serves only our property (the previous front yard based stop clock developed a minor leak and was removed). Therefore, seeing as we can use this without disruption to other houses, wouldn’t it effectively serve the same purpose as MikeG’s solution of moving the stop clock to the front wall, i.e. can cut off mains supply prior to running through the sub floor void?

 

[Marineboy]

So why not just rely on the water board stop cock outside the house?

 

[sunnybob]

The water board valve should be as close to the main as possible. If a leak developed between the main and the valve placed at your front door there could be a lot of damage to your property before the main supply could be cut.
Not much point having two valves only seperated by the thickness of the wall.

 

[J_Ashley]

Hopefully the attached schematic helps make things clearer.

With the exception of a short length of plastic pipe where the original stop cock was removed, the mains supply between the front and rear stop puffins (dark blue/purple dots) is the original lead pipe that we are looking to replace. The new stop cock at the front is solely for our property, and the rough distance between stop puffins is 13-15m

 

[flying haggis]

if the plastic pipe is run across the top of the floor void it could get chewed by rodents

 

[MikeG.]

As is usual, I need to make sure I’ve actually understood all the comments here….

Pipe lain across sub floor void:
- Less invasive, and so doesn’t have concerns associated with moling underneath the house.
- Risk of leaks means potential water damage to sub floor area, as the stop clock is located after this in the kitchen.

Mike G, Is my below interpretation of your methodology correct?

Mike G Solution:
- Mole (excavation is also possible as it’s only a 3-4m front yard) from property boundary to the front exterior wall at minimum depth of 750mm.
- Add new stop clock at front wall of the house.
- Plumb from new stop clock to current kitchen entry point, removing old stop clock in the process.
- My interpretation is that this is similar to the ‘Pipe lain across sub floor void’, but moves the stop clock to before the sub-floor void run thus giving protection in the event of a leak.

One detail that might be useful – whilst the property is Victorian, the stop clock on the pathway is modern and serves only our property (the previous front yard based stop clock developed a minor leak and was removed). Therefore, seeing as we can use this without disruption to other houses, wouldn’t it effectively serve the same purpose as MikeG’s solution of moving the stop clock to the front wall, i.e. can cut off mains supply prior to running through the sub floor void?

No, you've missed the principle point. The new stop cock would be on the inside of the house at the point the pipe enters. So the pipe would come in at low level, then be turned up the inside of the external wall, and where it goes above floor level you place a new stop cock. (No ifs or buts, you need your own internal stopcock). The new stopcock position is then plumbed across to meet the old one (which is removed), but above floor level. This could be below the kitchen units, for instance, but it should not be below the floor.

 

[J_Ashley]

No, you've missed the principle point. The new stop cock would be on the inside of the house at the point the pipe enters. So the pipe would come in at low level, then be turned up the inside of the external wall, and where it goes above floor level you place a new stop cock. (No ifs or buts, you need your own internal stopcock). The new stopcock position is then plumbed across to meet the old one (which is removed), but above floor level. This could be below the kitchen units, for instance, but it should not be below the floor.

Many thanks for the correction in my understanding. Seeing as the internal plumbing across to the old stock cock location should be above floor level, do you have any advice on avoiding something unsightly? To make it from the front wall to the kitchen it’s going to have to pass almost the entire length of the downstairs, through the open plan lounge/dining room/stairs area.

 

[MikeG.]

Without seeing your house, I couldn't possibly comment.

 

[J_Ashley]

but above floor level.

Just to clarify, by ‘but above floor level’ do you mean absolutely above the floorboards, or can it be below the floorboards but suspended off the very base/ground.

 

[MikeG.]

If you run it around below the floorboards (ie notched into the joists), it should be A/ above the insulation B/ in copper, and C/ accessible. This would be very much a second-best solution. Cold water pipes produce lots of condensation, so there will be permanent damp in the floor, however well lagged it is. More importantly, if it leaks, how will you ever know?

What happens to the existing main supply after the (internal) stop cock? Does the pipe go up to the first floor, or run around downstairs?

 

[J_Ashley]

What happens to the existing main supply after the (internal) stop cock? Does the pipe go up to the first floor, or run around downstairs?

Fortunately we have quite a few raised floorboards so we’ve been able to inspect. After the internal stop cock (kitchen) the water appears to be piped directly upstairs, where it splits to feed back down to the boiler or go to the bathroom.

 

[MikeG.]

What happens to the existing main supply after the (internal) stop cock? Does the pipe go up to the first floor, or run around downstairs?

Fortunately we have quite a few raised floorboards so we’ve been able to inspect. After the internal stop cock (kitchen) the water appears to be piped directly upstairs, where it splits to feed back down to the boiler or go to the bathroom.

In which case, would it be practical to bring your new supply in at the front wall and go straight up to the first floor to connect with the rising main up there (rather than down at the old stop cock location)?

 

[J_Ashley]

In which case, would it be practical to bring your new supply in at the front wall and go straight up to the first floor to connect with the rising main up there (rather than down at the old stop cock location)?

It’s certainly something to think about. At our boundary the mains is currently towards the side of our property with the front door and the stairs, and the front wall in the hall might make for a more subtle place of locating the interior stop cock.

Running vertically up to the 1st floor would bring it out in the front bedroom, and the rising main is in the rear bedroom so there would still have to be careful consideration regarding how to keep the pipe neat and tidy above the floor.

 

[MikeG.]

It wouldn't need to be above the bedroom floors. It could safely run in the ceiling (ie through the 1st floor joists). That's absolutely standard.