Renovation and extension works will inevitably involve stripping out old pipework to update or redirect plumbing runs, making it the perfect time to fix any niggling concerns. Here we take a look at the most common plumbing problems, and how to solve them.

Too many of us put up with bad plumbing — low water pressure, fluctuating temperatures, slow drainage, or exposed pipework. But while the evidence of a problem is clear to see, the cause can be harder to diagnose — often a result of a badly designed system or one which has been thoughtlessly extended but not upgraded. The good news is that many problems are inexpensive to fix when renovation work is already being carried out.

Exposed Surface Mounted Pipework

Concealing the pipework will usually involve completely removing the existing system and replacing it with new runs beneath the floorboards, and within the walls.

If walls cannot be chased out (for instance because the building is listed or of traditional construction such as lathe and plaster) pipe drops can be concealed within cupboards or boxed in within the new service ducts.

Plastic plumbing (Hep2O or JG Speedfit) can be easier to work with than rigid copper, as it is flexible and so can be threaded through joists and around obstacles without needing joints at every turn.

Poor Hot Water Supply

If the problem is low hot water pressure because the system is gravity fed (header tank), this could be improved by adding a pump to the system. A better option is to fit a pressurised hot water system, using either an unvented cylinder or a combi boiler, but this is only possible if the local mains pressure is at least 3 bar.

If the problem is poor hot water flow rate, it is likely that there is an undersized combination boiler — a common problem where a new bathroom has just been fitted, adding to hot water demand. The solution is to upgrade the boiler to a higher output model sized to match the demand, or to switch to a boiler and unvented cylinder.

Low Cold Pressure

If your rising mains pressure is low (at the kitchen tap), consider upgrading the size of connection into the property from the mains to improve the flow and reduce pressure loss. Properties built before 1970 that have not been updated since may still be connected to the mains by lead piping, and it is a good idea to replace this with plastic.

Taps Take Forever to Run Hot

With a combi boiler system there is little you can do to improve the time that hot water takes to reach a remote bathroom other than fit a separate water heater, or perhaps an electric shower.

Where there is a store of hot water (a cylinder or thermal store) it is possible to get almost instant hot water at every tap, no matter how far from the cylinder, by connecting them all from a circulating loop, with hot water flowing around it continually, powered by a bronze pump. To reduce heat loss, the pump could be put on a timer.

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Drain Smells Escape from Waste

If the fall from a basin is too great immediately after the waste trap, self-siphonage can occur, draining the water air lock in the trap, allowing drain smells to be released. To solve the problem, the fall should be reduced.

If a vacuum forms within the waste pipes because insufficient displacement air is being drawn in via the vent pipe, this can also pull traps dry and release foul smells.

This can occur if several fittings (basins, shower and bath) flow into the same waste pipe before it reaches the soil stack, and the pipe becomes full (especially on long, shallow pipe runs). The solution is to fit anti-siphon traps.

Waste Does Not Drain

Extending the waste pipe network to add new fittings is usually straightforward, and the Building Regulations (see for full details) clearly show the minimum fall and maximum distance to the soil stack required for each type of fitting (basin, WC, bath, shower etc.) to ensure waste water flows away freely. If a fitting is not draining it is either blocked, at the wrong gradient, or getting insufficient displacement air.

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No Stopcock

If there is no stopcock in the property you can turn the water supply off at the mains stopcock, usually located just outside the property. If the stopcock has been replaced by a water meter there is usually a lever next to it to cut off the supply. Fit a stopcock as part of your upgrade.

Connecting Cast Iron Soil Pipe to Plastic

Connecting together modern 100mm plastic soil pipes with old cast iron soil pipes can be achieved using rubber connectors fitted with jubilee clips to ensure a water and airtight seal (from

No Soil Pipe Nearby

The waste pipes for new bathrooms, a cloakroom or a kitchen are ideally connected into an existing soil and vent stack. If the distance is too great or the route not practical, a new soil and vent stack can usually be added either inside (possibly with an air inlet valve) or outside the property, provided there is a sewer outside to connect into and space for a new inspection chamber to connect into it.

If there is no accessible sewer, then a flexible small bore soil pipe, through which sewage is pumped after being macerated, is the best option (see for more). This will allow a bathroom to be fitted anywhere, even in a basement.

My Extension Will Go Over an Existing Inspection Chamber

You can build over an existing drain inspection chamber but you need to make sure it remains accessible in case of future blockages. You will also need to replace the cover with a vacuum-sealed cover.

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Old Copper Plumbing Has Earth Wires Connected to It

All copper pipes in and out of the boiler and heating system need earth bonding — also known as ‘equipotential bonding’ and ‘cross bonding’. Earth bonding will ensure that if a fault should occur, causing the metal plumbing, bath, taps, radiators, boiler casing to become live, this will not lead to electrocution.

The old earth cables can be safely disconnected, but copper sections of your new plumbing will still need to be cross bonded. If you use plastic pipe instead of copper, you do not need to earth appliances but you still have to earth the mains stopcock.

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