What is an Upside Down House.
For the purposes of this blog an upside down house is a house on multiple levels with a hot water cylinder on the ground floor. For cold water it is normal to supply all floors in such houses from a cold water pipe connected to the cold water tank in the loft. For hot water it is normal to supply all floors from a hot water pipe connected to the hot water cylinder through a pipe that doubles up as a vent pipe as well.
The problem in boosting a combined hot pipe is that adding pressure to a vent pipe will simply pump hot water into the cold water tank. There are several boosting solutions.
OPTION 1
Boost the individual hot and cold pipes close to the showers and taps you need to boost.
OPTION 2
Install a separate vent pipe from the hot water cylinder into the top of the cold water tank.
You will find the hot and cold water pipes are boxed in and there is a clear route all the way from the ground floor to the loft.
Cap off the existing vent pipe so that the existing pipe which was a combined feed and vent pipe is now a dedicated feed pipe so you can boost this pipe. A single boost SP2B (£125) fitted on the dedicated feed pipe near the cylinder should suffice.
Option 3 (my preferred option)
Install a separate vent pipe from the hot water cylinder into the top of the cold water tank.
You will find the hot and cold water pipes are boxed in and there is a clear route all the way from the ground floor to the loft.
Cap off the existing vent pipe so that the existing pipe which was a combined feed and vent pipe is now a dedicated feed pipe so you can boost this pipe. A double boost SP21S (£155) is fitted on the dedicated feed pipe near the cylinder. If you can change the gravity cold feed to a mains pressure feed then this solution gives you the equivalent of mains pressure hot and cold.
General Observation
Many plumbers who fit a hot water cylinder on the ground floor install a single pipe from the hot water cylinder to act as a vent and a hot feed. They may also have a single pipe which takes water from the cold water tank to feed all your taps and showers and also feeds the bottom of the hot water cylinder. Boosting a cold pipe which feeds the bottom of the hot water cylinder will drive hot water into the cold water tank. Boosting a hot pipe which vents into the cold water tank will drive hot water into the cold water tank.
A pipe which runs from the cold water tank to the bottom of the hot water tank needs to be 22mm.
The vent pipe should be 15mm but 10mm will also work.
