I need to take a new feed from my cold water cistern in the loft in order to hook up a power shower so I've bought a tank connector from Wickes. It didn't come with any washers, which I assume I need. Is this correct? If so, what sort - they sell all kinds, leather, rubber etc (I am still talking about Wickes here by the way). I assume I need to use PTFE on the thread of the connector. Is it also worth using some kind of sealant (silicone, plumbers mait, etc) to ensure a bombproof seal?
Also, as it's only a 15mm connector (it will only be used for the shower), I haven't seen a holesaw that will make a small enough hole. The tank is plastic - will a flat wood drill bit work, or will it result in me having to buy a new cistern?
If so, it should have a flat flexible washer with it - normally black.
You don't need PTFE tape on it. Generally what I do is to put some silicone sealer on the flange and insert into the hole, together with the washer, some silicone one the outside and then the nut.
There are normally two small brass lugs on the inside flange which are used for grippers for doing all this up.
Leave the outside nut slightly loose and complete the plumbing into the compression fitting on the outside. With grippers on the lugs inside, and the outside nut slightly loose, do up the compression nut. Then, keeping the grippers in place, tighten the outside nut onto the tank. This needs to be done before the silicone cures.
Strictly, silicone shouldn't be necessary, but I prefer belt and braces. Certainly try to avoid disturbing the connector afterwards,
One important thing is to make sure that you position this cold feed for the shower at a level on the tank below that for the hot water feed to the cylinder. That way, if the tank empties for any reason, the water goes cold rather than hot.
If the HW feed pipe is already low, then make it the shower one, and put a new connector at a higher point for the HW.
You don't want to risk a spade bit for this. It's something that you might get away with, but the consequences of not doing so will be tearful. There is a high risk of tearing an odd shaped hole.
You can get tank cutters from B&Q etc. I prefer the type that have thick metal cutters that screw onto a mandrel, rather than the cheap ones with springy steel concentric cutters - the former are far more accurate. Either you can buy a set of these cutters in a box, or individually. The size will be a bit bigger than 15mm for the tank connector, though, so I would measure it carefully.
One final question. Is the distance short? If not, then 22mm rather than 15mm for hot and cold could be better
When it comes to tasks like this, is it better to use silicone or plumbers mait? I've got some of both - the silicone (from Wickes) says it's not suitable for permanent submersion it water. Is this just because I've bought the cheap stuff, or is this normal?
I've got some leather washers - will they do the job? What's the difference between leather ones and rubber ones?
The distance is fairly short - basically the tank is more or less directly over the airing cupboard, so the pipe will go down there, then straight through the wall into the back of the shower. Probably not more than about
It may be acrylic sealer rather than silicone. Silicone sealer gives off a smell of acetic acid as it cures. I would use this rather than plumber's mait.
They may be, but I've always used the rubber ones because they came with tank connectors that I've bought.
Also watch that not too much force from the pipe work and pipe work moving is applied to the tank connector. In my last house the connecting pipe "jumped/moved" when the power shower was turned on and off and over time split the tank very slighty leading to the tank emptying out into the loft whilst on holiday.... Not nice to come back to.
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