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Plumbing in a cistern
Difficulty Cost

   Contents
  Introduction

 

The most popular replacement is the circular 227 litre (50 gallon) polyethylene cistern. This is because the cold water storage cistern is normally situated in the loft and this type of replacement cistern can be folded to pass through the narrow hatchway to the roofspace. The cistern supplies all the cold water taps in the house apart from the drinking water tap as well as the hot water cylinder.

Removing the old cistern

All water heating appliances should be switched off. Shut off the stopcock on the rising main. Turn on the cold taps in the bath and bathroom sink as this will help to empty the cistern by draining. There will be a little water left at the bottom of the cistern, and this should be removed using a small container to bail out the remainder. As the fitting could prove difficult to remove, a little oil will often help, at the fitting you are attempting to dismantle. Using a spanner, dismantle the distribution pipes, the overflow and the float valve. Move the old cistern out. If it is too big to remove from the roofspace, pull it to one side.


 
  Method

 

Prepare the location

Check the seating of the new cistern. The base should be firm and supported by a platform built across the joists. The platform should be nailed securely to the joists.

Commence plumbing in the new cistern

75mm (3 inches) below the top of the cistern cut a hole for the float valve to pass through. Put a plastic washer onto the tail of the float valve and pass it through the hole. Place the reinforcing plate onto the tail, then another washer and a fixing nut. Now tighten the fitting with your fingers until tight. Then use two spanners to tighten the fitting. A tap connector should now be screwed onto the valve, ready for the connection to the 15mm (0.5 inches) rising main.

Drill a second hole 25mm (1 inch) below the inlet for the float valve in order to connect the overflow pipe. Pass the connector through the hole. Now fit a washer and tighten its fixing nut on the inside of the cistern. Fit the insect filter and the dip pipe. A length of plastic overflow pipe needs to be attached to the assembly, run to the floor and then to the outside of the house, where it must be positioned in a conspicuous location. It is important to check the positioning of this pipe as continuous fall must be maintained.

Drill holes 50mm (2 inches) above the bottom of the cistern for each tank connector, to the hot water cylinder and the cold taps. Push the tank connectors through each hole with one polyethylene washer on the inside. Wrap a couple of turns of PTFE tape around the threads and fit the other washer. To stop the tank connector from turning, screw on the nut, but be careful not to overtighten as you could damage the washer and this could cause leakage. At this stage it is prudent to fit a gate valve to each distribution pipe. This will enable the you to cut off the water supply without having to empty the cistern.

Check the alignment of both the rising main and the distribution pipes to the system before connecting with compression fittings. Remember that if the cistern is plastic, soldered joints are unsuitable.

Final steps.

Clip all pipework to the joists to avoid movement as water passes through the cistern. Open the main stopcock, checking for leakage as the system fills. The float arm needs to be adjusted as the level of water rises, to maintain a water level 25mm (1 inch) below the overflow outlet. The vent pipe from the hot water cylinder should be adjusted to pass through the hole in the lid.


 
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  Comments
SubjectPosted by Replies Posted at
Forum Topic Replace old cistern with dual flush Silky10 3 24 Oct 07 at 13:34
Forum Topic Cistern - push button Toilet mcrobbo 2 03 Oct 07 at 15:29
Forum Topic water pipe ian3715 2 18 Sep 07 at 23:51
Forum Topic water pipe ian3715 1 18 Sep 07 at 23:50
Forum Topic Leaking 1950\\\'s cistern meddyuk 8 24 Aug 07 at 10:27
Forum Topic Fitting a Dudley Niagara Dual Flush Valve spartak96 11 11 Aug 07 at 9:42
Forum Topic cistern lonnie 6 18 Jul 07 at 16:05
Forum Topic Push button toilet 9lancer 2 30 May 07 at 15:03
Forum Topic old and new nuts malvo 14 22 May 07 at 17:34
Forum Topic Leaking Cistern p_maidment78 2 12 Feb 07 at 18:52
Forum Topic noisy cistern arnold1 0 11 Feb 07 at 21:14
Forum Topic new cistern deonve 2 09 Feb 07 at 10:16
Forum Topic Non Flushing Toilet Cister Grader 4 17 Dec 06 at 18:23
Forum Topic central heating vinitharatne 4 13 Dec 06 at 18:13
Forum Topic Ball cock vibration plumbduff 1 03 Nov 06 at 11:45
Forum Topic Why do I have a Cold water tank? auditerman 4 12 Oct 06 at 17:59
Forum Topic leak from bottom of cistern pcorpe 10 23 Aug 06 at 8:11
Forum Topic Cistern morpheus 2 28 Jun 06 at 21:03
Forum Topic cistern andrewh 5 14 May 06 at 18:10
Forum Topic Toilet Filter cabbagegreen 19 05 May 06 at 16:02
Forum Topic duel flush problem lenallen 2 07 Mar 06 at 18:59
Forum Topic Dripping overflow pipe mburdett 12 25 Feb 06 at 12:33
Forum Topic heat store trisers 0 20 Feb 06 at 18:11
Forum Topic rocca centre flush systern lenallen 4 12 Feb 06 at 10:38
Forum Topic Help please! Hefner 3 16 Nov 05 at 22:08
Forum Topic leaking overflow albackus 15 10 Oct 05 at 17:17
Forum Topic hot water cylinder carson 4 26 Jun 05 at 18:08
Forum Topic Overflowing cistern Tabbi 1 04 May 05 at 21:09
Forum Topic Stop valve leak rubio 4 23 Feb 05 at 16:42
Forum Topic Flushing cistern Burt 1 27 Jun 04 at 15:11
Forum Topic Overflow from Expansion Tank DaveB511 15 06 Jun 04 at 0:07
Forum Topic Old cistern caroleann67 2 17 Feb 04 at 22:05
Forum Topic cistern & cylinder petermays 1 14 Jan 04 at 16:01
Forum Topic CISTERN DANA 4 14 Jun 03 at 1:41


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