Critical pipe analysis

[Colin Blackburn]

I need to build a small pipe network with several ball valves to control water destination and its route. Here's the background.

Our water supply is from a spring and is normally enough for our needs. We have a borehole supply as a stand-by for very dry summers. We've never needed to use this but it needs to be available. In addition the borehole is used to supply water to the neighbouring farmer's sheep and the garden if our butts are empty. The water in the borehole is filtered to take out the iron. The process of using the borehole supply goes something like this:

1. Run water directly from borehole into ditch until it runs clear (viewed via a glass pipe in the network.)

1. Run water to destination via filter, one of: holding tank for house supply, tank in field for sheep, tank in garden for plant watering

2. Backflush the filter by running water through filter in reverse and into ditch for same length of time as 2.

The pipe network has, up until now, been made of PVC-U fittings (George Fischer grey pipes) with a series of ball valves. Last winter some pipes cracked---my fault for not draining a section---and so much of it needs to be replaced as it is made up of cemented connections rather than threaded or pushfit connections.

Some of the pipes going to the final destinations are the blue pipes (MDPE?) with a adaptors being used. Everything is pretty much one inch bore. I don't know what the pressure is but the MDPE connectors cope okay.

The filter has a single in and a single out connector using 1 inch threaded metal pipes but there are adaptors available to both the PVC-U and the MDPE.

Now, I could just rebuild the previous layout by buying various spares from George Fischer (RS don't quite stock the full range I need) but the valves are fairly pricey and there's a lot of cementing to do.

I have two questions, one a logic puzzle, the other a technical question.

First what is the minimum number of ball valves or taps that I need to accomplish every option (given any number of pipes, elbows, tees and crosses?)

The five paths are: Borehole -> Ditch (avoiding filter) Borehole -> filter -> holding tank Borehole -> filter -> field Borehole -> filter -> garden Borehole -> (filter backwards) -> ditch

It's this last requirement that bumps up the number I think.

Second, as I can't second guess why the original occupant chose PVC-U, what other piping systems should I consider?

It seems to be the valves/taps that cost the money so a system with the fewest, cheapest taps would be the cheapest option.

Incidentally, I know the current layout and number of taps but I thought I'd not prejudice any novel answers at this stage.

Colin

[Baz]

Hi Colin. I would do it with 3 on/off ball valves and 3 3way ball valves. I think I would use copper tube and solder joints and brass valves. Problem. When you are back flushing (I take it that you are using bore hole water) you are getting contaminates on the "Clean" side of the filter. Baz. Do I win a prize?

[Mike]

Spring and borehole water is often acidic and copper pipe lasts months at most. Have it tested or use only plastic parts.

What filter do you use for the iron and is it effective ?

[Colin Blackburn]

I'd have to check. The filter medium is a granular substrate, the filter itself is a 4 feet high cylinder filled with this stuff.

Is it effective? Well at a visual inspection level it is, beyond that I don't know. None of the farmer's sheep have ever died!

Testing both water supplies is on the cards for this summer.

Colin

[nightjar]

...

Try looking at swimming pool equipment. Mine has one six-position valve to the filter that IIRC would cope with that. However, as it is at the other end of France, I can't check that right now.

Colin Bignell