Moving a Hot Water Cylinder & Cold Water Tank

I'm in the process of moving my hot water cylinder and cold water tank to a new location. Things are going well but I have a couple of questions:

1) Should the cold water tank be directly above the hot water cylinder? It was in it's old position. In the new position it's nearer to an outside wall and the loft has a pitched roof. This means the tank will be about 1.5 metres to the left of the cylinder below. Will this reduce the head from the tank if the 22mm output from the tank takes a straight run across the floor before it drops down to the cylinder ? My guess is it makes no difference. It's the distance between the top of the water in the cold tank and the bottom of the hw cyl that's important.

2) I understand the vent pipe must be on a continual upward slope to work properly and prevent air locks. If it's a longer run to the tank does this matter so long as it's sloping upwards?

3) I've bought a Polytank PT2000 package from Screwfix and I need to drill 27mm holes in the cold water tank. The adjustable tank cutters i've found all say they make holes from 30mm upwards. I also have a hole saw but the blades on this go up in 5mm increments (25mm, 30mm etc). I've seen others in this forum have bought a Polytank. How did you cut your tank holes guys ? I have the 25 gallon version of the Polytank.

4) Any tips on tightening the hot water cylinder connections without causing damage? It's foamed on the outside which makes gripping the back of the connector with a second spanner (for the male connections) just about impossible. I'm going to use PTFE on the threads. Do I just do them up tightish without putting stress on the tank and that should be sufficent ? I have no problem with the side of the connector that has compression joints it's just the connections to the tank itself.

Thanks for any help with this.

Andy.

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Andy Hide
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It won't make a huge difference, but since you are doing this exercise, it's worth increasing the feed pipe size to 28mm to reduce the effect of the extra length especially if you might run a bath, shower and other services. I did this during a cylinder and tank change and it made an improvement. For bends, I used pairs of obtuse elbows with a short length of straight pipe between them. This gives less flow resistance than elbows and saves getting a large pipe bender. This approach also makes it easier to maintain slopes.

Not really. THis length is OK. Try and slope it upwards by at least

50-70mm over the 1500mm length.

Don't use concentric bimetal hole saw cutter sets for this because they are likely to wreck the tank unless you are extremely careful. The separate cutter types tha screw onto a mandrel are much better and you can certainly buy 27mm. B&Q have them as do the usual online places.

I put a smear of clear silicone sealer on each side of the tank connector fitting where it goes into the tank.

You can buy specific cylinder connectors (BES have them) but they aren't absolutely necessary. Provided that you wrap about 5-6 turns of tape along the thread neatly, you then screw the fitting on. There is no need to go mad with tightening it against the end limit because that doesn't make the seal anyway.

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Andy Hall

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